Case Interview Formulas: Key Concepts You Need to Know

If you’re preparing for a consulting case interview, you already know that numbers play a big role. Case interviews aren’t just about coming up with creative business solutions—they test your ability to analyze problems, break down calculations quickly, and structure your thinking like a consultant.

Many candidates get nervous about the math component, but the good news is that you don’t need to be a human calculator. You just need to understand a set of core formulas that consulting firms use regularly. Once you know these, you’ll be able to approach case questions with confidence, make data-backed recommendations, and show interviewers that you think like a consultant.

In this guide, you’ll learn:

The essential formulas for case interviews and why they matter
How to apply these formulas in different types of business problems
Common mistakes to avoid when working with numbers in case interviews

Let’s start by understanding why knowing these formulas is so important.

Why Case Interview Formulas Matter

Picture yourself in a case interview. The interviewer asks you to estimate the profit margin of a company launching a new product. You hesitate for a moment, unsure how to start. Should you focus on revenue? Costs? Market share? If you don’t have a structured approach, you might waste time figuring out where to begin.

This is where knowing the right formulas helps. By understanding key business calculations, you can:

Save time during the interview by quickly plugging in numbers
Show a structured, logical approach that mimics how consultants think
Reduce mistakes by relying on proven business calculations
Focus on insights instead of getting stuck on calculations

Think of these formulas as tools in your problem-solving toolkit. The more familiar you are with them, the easier it will be to navigate any case problem you encounter.

Profitability Formulas

Profitability is one of the most common areas tested in case interviews. Consulting firms often help clients improve their bottom line, whether by increasing revenue, reducing costs, or optimizing pricing strategies. Understanding how to calculate profit and assess financial performance will help you break down business problems efficiently.

Here are the key profitability formulas you need to know.

1. Revenue Calculation

Revenue represents the total amount of money a company earns from selling its products or services. It’s the starting point for most business calculations because every company needs to generate revenue to cover costs and make a profit.

Formula:
Revenue = Price × Quantity

Example Usage:

Question: A company sells office chairs for $150 each. Last year, they sold 5,000 chairs. What was the company's total revenue?

Answer:
Revenue = 150 × 5,000
Revenue = $750,000

2. Total Variable Costs

Variable costs are expenses that change depending on how many units a company produces or sells. These include costs like raw materials, packaging, and shipping. Understanding variable costs is important because they directly affect profit margins.

Formula:
Total Variable Costs = Quantity × Variable Cost per Unit

Example Usage:

Question: A bakery spends $2 on ingredients for each loaf of bread it makes. If it produces 10,000 loaves a month, what are the total variable costs?

Answer:
Total Variable Costs = 10,000 × 2
Total Variable Costs = $20,000

3. Total Costs

Every business has both variable costs and fixed costs. Fixed costs, like rent and salaries, don’t change regardless of how many units a company sells. The total cost formula combines both types of expenses to calculate the overall cost of running the business.

Formula:
Total Costs = Total Variable Costs + Fixed Costs

Example Usage:

Question: A retail store pays $50,000 in rent per year and has total variable costs of $200,000. What are the store’s total costs?

Answer:
Total Costs = 200,000 + 50,000
Total Costs = $250,000

4. Profit Calculation

Profit is what remains after subtracting all costs from revenue. A company’s goal is to maximize profit by either increasing revenue or reducing costs. This formula is at the core of many consulting case problems, as firms often help businesses improve profitability.

Formula:
Profit = Revenue – Total Costs

Example Usage:

Question: A technology startup generated $1.2 million in revenue last year. Its total costs were $900,000. What was the company’s profit?

Answer:
Profit = 1,200,000 – 900,000
Profit = $300,000

5. Profit Margin

Profit margin tells you what percentage of a company’s revenue turns into profit. It’s a key indicator of a company’s financial health and efficiency. A higher profit margin means a company is making more money relative to its revenue.

Formula:
Profit Margin = (Profit / Revenue) × 100

Example Usage:

Question: A consulting firm earned $500,000 in revenue and made a profit of $75,000. What is its profit margin?

Answer:
Profit Margin = (75,000 / 500,000) × 100
Profit Margin = 15%

6. Contribution Margin

The contribution margin helps businesses determine how much each unit sold contributes to covering fixed costs and generating profit. It’s useful for understanding pricing decisions and profitability per product.

Formula:
Contribution Margin = Price – Variable Cost per Unit

Example Usage:

Question: A software company sells a subscription for $50 per month. The variable cost per customer (customer support and server costs) is $10 per month. What is the contribution margin per customer?

Answer:
Contribution Margin = 50 – 10
Contribution Margin = $40 per customer

These profitability formulas form the foundation of many case interview questions. Being comfortable with them will help you break down business problems, make quick calculations, and provide structured recommendations.

Market Analysis Formulas

Market analysis is a key component of consulting case interviews. Understanding a company’s position within the market, growth potential, and competitive landscape helps you provide strategic recommendations. Many case problems require estimating market size, evaluating a company’s performance relative to competitors, or analyzing growth trends.

Here are the essential market analysis formulas you need to know.

1. Market Share

Market share measures a company’s sales as a percentage of total market sales. It helps assess a company’s competitive position and how much influence it has in the industry. A company with a high market share typically has strong brand recognition and customer loyalty.

Formula:
Market Share = (Company Revenue / Total Market Revenue) × 100

Example Usage:

Question: A smartphone company generates $10 billion in annual revenue, while the total market revenue for smartphones is $100 billion. What is the company's market share?

Answer:
Market Share = (10B / 100B) × 100
Market Share = 10%

2. Relative Market Share

Relative market share compares a company’s market share to its largest competitor. It helps determine whether a company is a market leader or a challenger in the industry.

Formula:
Relative Market Share = Company Market Share / Largest Competitor’s Market Share

Example Usage:

Question: A beverage company has a 25% market share, while its largest competitor holds a 50% market share. What is the company's relative market share?

Answer:
Relative Market Share = 25% / 50%
Relative Market Share = 0.5 (or 50%)

3. Market Size Estimation

Market sizing is a common case interview exercise where you estimate the potential revenue of an industry or a specific market segment. It helps businesses understand the total demand for their product or service.

Formula:
Market Size = Target Population × Penetration Rate × Average Revenue per Customer

Example Usage:

Question: You are estimating the market size for premium coffee subscriptions in the U.S. There are 100 million coffee drinkers, 10% of whom are willing to pay for a premium subscription. The average subscription costs $20 per month. What is the annual market size?

Answer:
Market Size = 100M × 10% × (20 × 12)
Market Size = 100M × 0.1 × 240
Market Size = $2.4 billion

4. Compound Annual Growth Rate (CAGR)

CAGR measures the average annual growth rate of a company’s revenue, profit, or market size over multiple years. It’s useful for tracking a company’s long-term performance.

Formula:
CAGR = [(Ending Value / Beginning Value)^(1 / Number of Years)] – 1

Example Usage:

Question: A company's revenue grew from $50 million to $100 million over five years. What is the CAGR?

Answer:
CAGR = [(100M / 50M)^(1 / 5)] – 1
CAGR = (2^(0.2)) – 1
CAGR ≈ 14.87%

5. Price Elasticity of Demand

Price elasticity measures how sensitive consumer demand is to changes in price. If demand changes significantly when prices increase or decrease, the product is considered highly elastic. If demand remains stable despite price changes, the product is inelastic.

Formula:
Price Elasticity = (% Change in Quantity Demanded) / (% Change in Price)

Example Usage:

Question: A fashion retailer increases the price of a jacket by 20%, causing demand to drop by 40%. What is the price elasticity of demand?

Answer:
Price Elasticity = (-40% / 20%)
Price Elasticity = -2

Since the absolute value is greater than 1, demand is elastic, meaning consumers are highly sensitive to price changes.

6. Cross Elasticity of Demand

Cross elasticity measures how the demand for one product changes in response to a price change in another product. This is useful for analyzing the relationship between complementary (used together) and substitute (competing) products.

Formula:
Cross Elasticity = (% Change in Quantity Demanded for Product A) / (% Change in Price of Product B)

Example Usage:

Question: A soft drink company raises its price by 10%, and as a result, demand for a competitor’s soft drink increases by 5%. What is the cross elasticity of demand?

Answer:
Cross Elasticity = (5% / 10%)
Cross Elasticity = 0.5

Since the result is positive, the two products are substitutes—when the price of one increases, demand for the other increases.

7. Rule of 72

The Rule of 72 is a simple way to estimate how long it will take for an investment or market size to double, assuming a fixed growth rate.

Formula:
Years to Double = 72 / Annual Growth Rate

Example Usage:

Question: A tech startup is growing its customer base at a rate of 12% per year. How long will it take for its customer base to double?

Answer:
Years to Double = 72 / 12
Years to Double = 6 years

Understanding market analysis formulas is crucial for assessing a company’s position, predicting future growth, and making strategic recommendations.

Investment Assessment Formulas

Investment assessment formulas help businesses evaluate financial decisions, determine the profitability of projects, and assess how long it takes to recover an investment. Consulting firms often help clients analyze investments to maximize returns and minimize risks. Knowing these formulas will help you make sound financial recommendations during case interviews.

1. Return on Investment (ROI)

Return on Investment (ROI) measures how profitable an investment is relative to its cost. It is one of the most widely used metrics in business, as companies invest in projects, marketing campaigns, and operational improvements with the expectation of generating higher returns.

Formula:
ROI = (Net Profit / Investment Cost) × 100

Example Usage:

Question: A company spends $100,000 on a new advertising campaign, resulting in an additional $200,000 in revenue and $50,000 in profit after deducting costs. What is the ROI of the campaign?

Answer:
ROI = (50,000 / 100,000) × 100
ROI = 50%

This means the company earned a 50% return on its investment.

2. Payback Period

Payback period calculates how long it takes for an investment to recover its initial cost. The shorter the payback period, the faster the investment becomes profitable.

Formula:
Payback Period = Investment Cost / Annual Profit

Example Usage:

Question: A company invests $500,000 in a new factory expansion. The expansion generates an additional $125,000 in profit annually. How long will it take to recover the investment?

Answer:
Payback Period = 500,000 / 125,000
Payback Period = 4 years

The company will recover its investment in 4 years.

3. Net Present Value (NPV)

Net Present Value (NPV) calculates the present value of future cash flows from an investment. A positive NPV means the investment is expected to be profitable, while a negative NPV suggests a loss.

Formula:
NPV = Σ [Cash Flow / (1 + Discount Rate)^Year] – Initial Investment

Example Usage:

Question: A company is considering a $200,000 investment that is expected to generate annual cash flows of $60,000 for five years. The discount rate is 10%. Should the company proceed with the investment?

Answer:
NPV = (60,000 / 1.1) + (60,000 / 1.1²) + (60,000 / 1.1³) + (60,000 / 1.1⁴) + (60,000 / 1.1⁵) – 200,000
NPV ≈ $37,905

Since the NPV is positive, the company should proceed with the investment.

4. Internal Rate of Return (IRR)

The Internal Rate of Return (IRR) is the discount rate that makes the Net Present Value (NPV) of an investment equal to zero. It represents the expected annual return on an investment. If the IRR is higher than the company’s required rate of return, the investment is considered attractive.

Formula:
IRR is the discount rate where:
NPV = 0

Example Usage:

Question: A company invests $50,000 in a project that generates $15,000 in cash flow per year for five years. The company’s required rate of return is 8%. Should it proceed with the investment?

Answer:
Using financial modeling or an IRR calculator, the IRR is found to be approximately 12%. Since 12% is greater than 8%, the company should proceed with the investment.

5. Return on Assets (ROA)

Return on Assets (ROA) measures how efficiently a company is using its total assets to generate profit. A higher ROA indicates better asset utilization and financial performance.

Formula:
ROA = Net Income / Total Assets

Example Usage:

Question: A company reports a net income of $2 million and has total assets worth $20 million. What is its ROA?

Answer:
ROA = 2M / 20M
ROA = 10%

This means the company earns 10 cents of profit per dollar of assets owned.

6. Perpetuity Formula

The perpetuity formula is used to calculate the present value of an investment that provides constant cash flows indefinitely. It is commonly used in valuing bonds, annuities, and long-term financial commitments.

Formula:
Present Value = Cash Flow / Discount Rate

Example Usage:

Question: A company receives $10,000 per year indefinitely from a fixed-income investment. The discount rate is 5%. What is the present value of this investment?

Answer:
Present Value = 10,000 / 0.05
Present Value = $200,000

The investment is valued at $200,000 in today’s terms.

Investment assessment formulas are crucial in evaluating financial decisions and making data-driven recommendations in case interviews.

Operational Efficiency Formulas

Operational efficiency is a key focus area for businesses looking to improve productivity, reduce costs, and maximize output. In case interviews, you may be asked to assess a company’s production capacity, efficiency, or cost-saving potential. Knowing how to calculate these metrics will help you provide data-driven recommendations.

Here are the essential operational efficiency formulas you need to know.

1. Break-Even Point

The break-even point is the number of units a company must sell to cover its fixed and variable costs. At this point, the company makes zero profit and zero loss. It is a crucial metric for determining the financial feasibility of a product or business.

Formula:
Break-Even Point (Units) = Fixed Costs / (Selling Price per Unit – Variable Cost per Unit)

Example Usage:

Question: A company has $100,000 in fixed costs and sells a product for $50 per unit, with variable costs of $30 per unit. How many units must it sell to break even?

Answer:
Break-Even Point = 100,000 / (50 – 30)
Break-Even Point = 100,000 / 20
Break-Even Point = 5,000 units

The company must sell 5,000 units to break even.

2. Utilization Rate

Utilization rate measures how efficiently a company is using its resources relative to their full capacity. A low utilization rate may indicate underused resources, while a high rate suggests near-maximum efficiency.

Formula:
Utilization Rate = (Actual Output / Maximum Possible Output) × 100

Example Usage:

Question: A factory can produce 1,000 cars per month at full capacity. Last month, it produced 800 cars. What was its utilization rate?

Answer:
Utilization Rate = (800 / 1,000) × 100
Utilization Rate = 80%

The factory operated at 80% of its full capacity.

3. Output Calculation

Output calculation helps measure production efficiency by estimating the total number of units produced based on the production rate and time available.

Formula:
Output = Rate × Time

Example Usage:

Question: A bottling plant fills 500 bottles per hour. If it operates for 16 hours per day, how many bottles are filled in a day?

Answer:
Output = 500 × 16
Output = 8,000 bottles per day

The plant produces 8,000 bottles per day.

4. Inventory Turnover Ratio

The inventory turnover ratio measures how efficiently a company sells and replaces its inventory. A higher ratio means faster inventory turnover, which is generally a good sign of strong sales.

Formula:
Inventory Turnover = Cost of Goods Sold / Average Inventory

Example Usage:

Question: A retail store has a cost of goods sold (COGS) of $500,000 and an average inventory value of $100,000. What is its inventory turnover ratio?

Answer:
Inventory Turnover = 500,000 / 100,000
Inventory Turnover = 5

This means the company sold and replaced its inventory five times over the period.

5. Labor Productivity

Labor productivity measures how efficiently workers produce goods or services. It is useful for assessing operational performance and workforce efficiency.

Formula:
Labor Productivity = Output / Number of Workers

Example Usage:

Question: A team of 20 workers produces 5,000 units per week. What is the labor productivity per worker?

Answer:
Labor Productivity = 5,000 / 20
Labor Productivity = 250 units per worker per week

Each worker produces an average of 250 units per week.

Operational efficiency formulas are essential for evaluating business productivity, resource allocation, and cost optimization in case interviews.

Pricing and Revenue Optimization Formulas

Pricing decisions directly impact a company’s revenue and profitability. In case interviews, you may be asked to evaluate pricing strategies, determine optimal pricing levels, or assess how pricing affects demand. Understanding these formulas will help you analyze how businesses can maximize revenue while maintaining competitive pricing.

1. Markup Percentage

Markup percentage measures how much a company increases the price of a product compared to its cost. It is commonly used in retail and manufacturing to determine the selling price.

Formula:
Markup Percentage = [(Selling Price – Cost Price) / Cost Price] × 100

Example Usage:

Question: A clothing retailer buys a jacket for $40 and sells it for $70. What is the markup percentage?

Answer:
Markup Percentage = [(70 – 40) / 40] × 100
Markup Percentage = (30 / 40) × 100
Markup Percentage = 75%

The retailer applies a 75% markup to the jacket.

2. Target Costing

Target costing is a pricing method where a company determines the maximum allowable cost for a product based on a desired profit margin. It is used to ensure that a product remains profitable while remaining competitively priced.

Formula:
Target Cost = Selling Price – Desired Profit

Example Usage:

Question: A company wants to sell a smartphone for $500 and maintain a profit of $150 per unit. What should be the target cost to ensure this profit margin?

Answer:
Target Cost = 500 – 150
Target Cost = $350

The company must keep production costs at or below $350 per smartphone to meet its profit goal.

3. Customer Lifetime Value (CLV)

Customer Lifetime Value (CLV) helps businesses estimate how much revenue they can expect from a single customer over the entire period of their relationship. This is particularly important in subscription-based and recurring revenue businesses.

Formula:
CLV = (Average Purchase Value × Purchase Frequency × Customer Lifespan)

Example Usage:

Question: A gym charges $50 per month per customer. The average customer stays for 24 months. What is the CLV of a gym member?

Answer:
CLV = 50 × 12 × 2
CLV = $1,200

Each customer contributes an estimated $1,200 in revenue over their lifetime.

4. Customer Acquisition Cost (CAC)

Customer Acquisition Cost (CAC) calculates how much a company spends to acquire a new customer. Businesses aim to keep CAC lower than CLV to ensure long-term profitability.

Formula:
CAC = Total Marketing and Sales Costs / Number of New Customers Acquired

Example Usage:

Question: A startup spends $100,000 on marketing and sales efforts in one year and acquires 2,500 new customers. What is its CAC?

Answer:
CAC = 100,000 / 2,500
CAC = $40

The company spends $40 to acquire each new customer.

5. Price Elasticity of Demand

Price elasticity measures how sensitive customer demand is to price changes. If demand changes significantly when the price increases or decreases, the product is considered elastic. If demand remains stable despite price changes, it is inelastic.

Formula:
Price Elasticity = (% Change in Quantity Demanded) / (% Change in Price)

Example Usage:

Question: A company increases the price of a software subscription from $10 to $12 per month, leading to a 20% decrease in subscriptions. What is the price elasticity?

Answer:
Price Elasticity = (-20% / 20%)
Price Elasticity = -1

A price elasticity of -1 means demand is unit elastic, meaning price and demand change proportionally.

6. Revenue Maximization Formula

Revenue is maximized when marginal revenue (MR) equals marginal cost (MC). In simpler cases, revenue maximization occurs when a company finds the optimal price and quantity balance to generate the highest possible revenue.

Formula:
Revenue = Price × Quantity

Example Usage:

Question: A company charges $20 per unit and sells 5,000 units per month. What is its total revenue?

Answer:
Revenue = 20 × 5,000
Revenue = $100,000

The company generates $100,000 in revenue per month.

Pricing and revenue optimization formulas help businesses balance profitability with competitiveness. In case interviews, using these formulas will allow you to analyze pricing strategies, assess revenue potential, and make data-driven recommendations.

Applying These Formulas in Case Interviews

Knowing the formulas is important, but understanding when and how to use them in case interviews is what truly sets strong candidates apart. Consulting firms expect you to apply these formulas within a structured approach to solve business problems. This section will guide you through how these formulas are used in real consulting case interview scenarios.

1. Profitability Analysis

Profitability is one of the most common topics in case interviews. You may be asked to analyze why a company’s profits are declining or recommend ways to improve profitability.

Example Scenario

A restaurant chain has seen its profit margin decline over the past year. The interviewer asks you to determine the root cause and suggest solutions.

How to Apply the Formulas

Start by calculating revenue using the formula: Revenue = Price × Quantity. Determine total costs by adding fixed and variable costs. Use the profit formula: Profit = Revenue – Total Costs. If profit margins are shrinking, break it down further to identify whether revenue is declining or costs are increasing. Use contribution margin analysis to assess whether each product is profitable.

Possible Recommendation

If costs are increasing, suggest negotiating better supplier contracts or reducing waste in operations. If revenue is declining, consider adjusting pricing strategies or launching new marketing campaigns.

2. Market Sizing and Growth Strategy

Market sizing questions test your ability to estimate the size of an industry or market using logical assumptions. These are often paired with growth strategy recommendations.

Example Scenario

A consulting firm wants to assess the total market size for electric bikes in the U.S. and provide recommendations for entry.

How to Apply the Formulas

Use the market size estimation formula: Market Size = Target Population × Penetration Rate × Average Revenue per Customer. Use CAGR to estimate how fast the market is growing over time. Use market share formulas to determine the client’s potential position in the industry.

Possible Recommendation

If the market is growing rapidly, recommend early entry to capture market share. If competition is intense, suggest differentiation strategies, such as targeting specific customer segments or offering unique features.

3. Investment Decisions

Investment-related case questions often involve analyzing whether a company should proceed with a financial decision, such as launching a new product or acquiring another company.

Example Scenario

A company is considering a $2 million investment in expanding its manufacturing plant. The interviewer asks if this is a good decision.

How to Apply the Formulas

Use ROI to determine if the investment will generate strong returns. Calculate the payback period to see how long it will take for the company to recover its investment. Use NPV and IRR to assess the project’s long-term profitability.

Possible Recommendation

If the investment has a positive NPV and a strong ROI, recommend proceeding. If the payback period is too long or the IRR is lower than the company’s required return, suggest alternative investment options.

4. Pricing Strategy Optimization

Pricing strategy cases often require you to determine the optimal price for a product or evaluate the impact of a price change on revenue and demand.

Example Scenario

A SaaS company is considering increasing its subscription fee from $50 to $60 per month but is concerned about potential customer churn.

How to Apply the Formulas

Use price elasticity of demand to estimate how sensitive customers are to the price change. Calculate the revenue impact using the formula: Revenue = Price × Quantity. Compare contribution margins before and after the price increase.

Possible Recommendation

If demand is highly elastic, the price increase may significantly reduce customer subscriptions, leading to lower revenue. In that case, suggest alternative revenue strategies, such as offering tiered pricing plans. If demand is inelastic, the company can safely raise prices without losing many customers.

5. Operational Efficiency Improvements

Some case interview questions test your ability to optimize a company’s operations, such as improving manufacturing processes or reducing costs.

Example Scenario

A car manufacturer is struggling with high production costs and underutilized factory capacity. The interviewer asks for recommendations.

How to Apply the Formulas

Calculate the utilization rate to assess how efficiently the factory is operating. Use break-even analysis to determine how many cars must be sold to cover costs. Evaluate inventory turnover to identify if excess inventory is tying up capital.

Possible Recommendation

If utilization is low, suggest optimizing production schedules or outsourcing certain processes. If inventory turnover is slow, recommend reducing excess stock or implementing just-in-time inventory practices.

Applying these formulas in case interviews demonstrates structured thinking, business acumen, and problem-solving ability. Next, let’s go over tips for improving speed and accuracy in case interview math.

Tips for Mastering Case Interview Math

Strong quantitative skills can set you apart in case interviews. While knowing formulas is essential, your ability to apply them quickly and accurately under pressure is what really matters. Many candidates struggle with mental math or misinterpret numerical data, leading to mistakes that weaken their analysis. The good news is that you don’t need to be a math genius to succeed—you just need the right strategies.

Here are some practical tips to help you improve your speed and accuracy when working with numbers in case interviews.

1. Develop Strong Mental Math Skills

Calculators are not allowed in case interviews, so being able to perform quick mental calculations is a must. While complex calculations are rarely required, you should be comfortable with:

Multiplication and division with large numbers, such as 240 × 35 or 12,000 ÷ 16
Percentages and ratios, like finding 15% of 240 or calculating profit margins
Estimations and rounding, such as simplifying 387 × 22 by approximating it as 390 × 20

One way to practice is by setting a timer and solving real-world business calculations daily, such as estimating discounts while shopping or calculating tips at restaurants.

2. Use Approximation and Rounding Wisely

Consultants rarely need exact numbers—approximation saves time without sacrificing accuracy. In case interviews, round numbers to make calculations easier, but keep them close to the real value.

For example, instead of calculating 387 × 22 precisely:

Round 387 to 390
Round 22 to 20
Multiply 390 × 20 = 7,800

The actual answer is 8,514, meaning the approximation is within 10% of the real value, which is acceptable for most case problems.

3. Structure Your Calculations Step by Step

A common mistake candidates make is rushing through calculations and making careless errors. Structuring your math ensures clarity and accuracy. Follow these steps when performing calculations:

Identify what needs to be calculated first.
Write down the formula you’ll use.
Plug in the numbers and simplify in stages.
Check whether the final answer makes logical sense.

For example, when calculating profit margin, instead of jumping to the answer immediately, follow a structured approach:

Step 1: Write the formula → Profit Margin = (Profit / Revenue) × 100
Step 2: Plug in numbers → ($75,000 / $500,000) × 100
Step 3: Simplify → 0.15 × 100 = 15%

This approach ensures that even under time pressure, you avoid mistakes and present your calculations clearly to the interviewer.

4. Memorize Key Business Benchmarks

Consultants often rely on commonly used business benchmarks to estimate values quickly. Having a few of these in mind can save time in case interviews. Some useful benchmarks include:

One year has 52 weeks or roughly 250 working days.
A month can be estimated as four weeks.
A company with a 10% profit margin earns $10 of profit for every $100 in revenue.
The rule of 72 helps estimate how long it takes for something to double in value.

By memorizing benchmarks, you can make reasonable assumptions and solve problems faster.

5. Practice Under Timed Conditions

Speed and accuracy improve with practice. Set a timer and try solving case math questions under time constraints. Start with simple calculations and gradually move on to more complex problems. Resources like case prep books, mental math apps, and business news articles with financial data can provide useful practice material.

6. Double-Check Your Answers

While speed is important, careless mistakes can cost you the interview. Always take a few seconds to check whether your answer makes sense. Look for these common errors:

Did you misplace a decimal?
Does the answer align with the expected range?
Did you use the correct formula?

If something feels off, quickly rework your calculation before presenting your answer.

Case interview math doesn’t have to be intimidating. With practice, structured thinking, and the right strategies, you can confidently handle numerical problems and impress your interviewer.

Common Pitfalls to Avoid in Case Interview Math

Even strong candidates can make mistakes in case interview calculations. The pressure of solving problems on the spot, combined with time constraints, can lead to errors that weaken your analysis. Understanding the most common pitfalls will help you avoid unnecessary mistakes and improve your overall performance.

1. Misinterpreting the Question

Many candidates jump into calculations without fully understanding what the interviewer is asking. This can lead to solving the wrong problem or using an incorrect approach.

If an interviewer asks you to determine profitability but you mistakenly calculate revenue, your entire analysis will be off. Always take a few seconds to clarify the objective before starting calculations.