Author: Taylor Warfield, Former Bain Manager and interviewer

Last Updated: May 28, 2026

Case interview formulas are the handful of business equations you need to solve the math in a consulting case. You do not need advanced finance or calculus. You need about a dozen core formulas memorized cold and a clear understanding of what each one means.

 

This article covers the 27 formulas that show up in consulting interviews, grouped from most to least common. Master the case interview math behind them and you can handle the quantitative portion of nearly any case at McKinsey, BCG, Bain, and beyond.

 

But first, a quick heads up:

 

McKinsey, BCG, Bain, and other top firms accept less than 1% of applicants every year. If you want to triple your chances of landing interviews and 8x your chances of passing them, watch my free 40-minute training.

 

What Changed in 2026?

 

This guide has been expanded with the breakeven and growth rate formulas, a quick-reference table that ranks every formula by how often it appears, a section on how to apply formulas inside a live case, and the most common math mistakes candidates make.

 

All formulas and worked examples have been reviewed for accuracy, and the formulas are now grouped by frequency so you know exactly which ones to learn first.

 

Which Case Interview Formulas Should You Learn First?

 

Learn the profit, revenue, cost, margin, breakeven, and growth formulas first. These appear in the vast majority of cases. The accounting, finance, and economics formulas at the end appear rarely, so learn them last.

 

Here is the full list ranked by how often each formula shows up in real interviews.

 

Formula	How Often It Appears
Revenue = Quantity x Price	Almost every case
Profit = Revenue minus Costs	Almost every case
Costs = Variable Costs + Fixed Costs	Almost every case
Profit Margin = Profit / Revenue	Very common
Contribution Margin = Price minus Variable Cost	Very common
Growth Rate = (New minus Old) / Old	Very common
Breakeven Quantity = Fixed Costs / Contribution Margin	Very common
Market Share = Company Revenue / Market Revenue	Common
ROI = Profit / Investment Cost	Common
Payback Period = Investment / Annual Profit	Common
Output = Rate x Time	Common
Utilization = Output / Maximum Output	Common
CAGR, NPV, EBITDA, elasticity, ROE, ROA	Rare

 

What Are the Profit Formulas for Case Interviews?

 

The profit formulas are the foundation of nearly every case. They let you break a company's profit into revenue and costs, then break each of those into smaller pieces until you find the root cause of a problem. These are the formulas you should know best.

 

They form the backbone of any profitability case, which is the single most common case type you will face.

 

1. Revenue = Quantity x Price

 

Revenue is the amount of money a company brings in from selling its products. You calculate it by taking the number of units sold and multiplying it by the price per unit.

 

Example: Your company sells shirts for $20 each. Last year, your company sold 1,000 shirts. So your total revenue last year was 1,000 x $20 = $20,000.

 

2. Total Variable Costs = Quantity x Variable Cost

 

Costs are the payments a company makes to run its business. There are two types of costs, variable costs and fixed costs.

 

Variable costs increase for each additional unit produced. They represent the cost of the raw materials needed to make the product.

 

You calculate total variable costs by taking the number of units produced and multiplying it by the raw material cost per unit.

 

Example: It costs your company $5 to buy the raw materials for one shirt. If your company sold 1,000 shirts last year, total variable costs are 1,000 x $5 = $5,000.

 

3. Costs = Total Variable Costs + Fixed Costs

 

Total costs equal total variable costs plus fixed costs.

 

Fixed costs do not increase for each additional unit produced. They include costs such as rent for the building or the equipment needed to make the product.

 

Example: Your company pays $10,000 in annual rent and leases its equipment for $2,000 a year, so fixed costs are $12,000. Total variable costs were $5,000 from the previous example. So total costs are $12,000 + $5,000 = $17,000.

 

4. Profit = Revenue minus Costs

 

Profit is the money a company keeps after paying for all of its costs. You calculate it by subtracting total costs from total revenue.

 

Example: Last year your shirt company generated $20,000 in revenue and had $17,000 in costs. Profit was $20,000 minus $17,000 = $3,000.

 

5. Profit = (Price minus Variable Cost) x Quantity minus Fixed Costs

 

This formula combines the previous four into one concise equation. It is useful when you want to see how a change in price, volume, or cost flows straight through to profit.

 

6. Contribution Margin = Price minus Variable Cost

 

Contribution margin is how much money each unit sold brings in after covering the raw material cost of that unit. It is the amount each sale contributes toward covering fixed costs.

 

Example: If your shirts sell for $20 and raw materials cost $5, the contribution margin is $20 minus $5 = $15 per shirt.

 

7. Profit Margin = Profit / Revenue

 

Profit margin is the percentage of revenue a company keeps as profit after all of its costs. It is one of the fastest ways to judge how healthy a business is.

 

Example: Last year your company generated $20,000 in revenue and had $17,000 in costs, for a profit of $3,000. So your profit margin is $3,000 / $20,000 = 15%.

 

What Are the Breakeven and Growth Formulas for Case Interviews?

 

Breakeven and growth formulas are two of the most commonly tested calculations after the core profit formulas. Breakeven tells you how many units a company must sell to cover its costs. Growth rate tells you how fast a number is changing over time.

 

8. Breakeven Quantity = Fixed Costs / Contribution Margin

 

The breakeven quantity is the number of units a company must sell so that total revenue exactly equals total costs. At this point profit is zero. Every unit sold beyond it is pure profit.

 

Since contribution margin equals price minus variable cost, you can also write the formula as Breakeven Quantity = Fixed Costs / (Price minus Variable Cost).

 

Example: A company has $600 in fixed costs and sells a product for $4 with a variable cost of $1. The contribution margin is $3, so the breakeven quantity is $600 / $3 = 200 units.

 

Before you calculate, always check that price is greater than variable cost. If it is not, the company loses money on every sale and breakeven is impossible. This setup appears constantly in new product and market entry cases, which is why breakeven analysis is worth practicing until it is second nature.

 

9. Growth Rate = (New Value minus Old Value) / Old Value

 

Growth rate measures how much a number, such as revenue or profit, has increased or decreased over a period. A negative result means the number shrank.

 

Example: Your company had $120M in revenue last year and $100M this year. The growth rate is ($100M minus $120M) / $120M = negative 17%. Revenue fell 17% year over year.

 

What Are the Investment Formulas for Case Interviews?

 

Investment formulas help you decide whether a company should spend money now to earn more money later. ROI and payback period are the two you will use most often when a case asks you to evaluate an investment.

 

10. Return on Investment = Profit / Investment Cost

 

Return on investment, or ROI, shows how much additional money a company generates relative to the size of its initial investment. You calculate it by dividing the profit from the investment by the investment cost.

 

Example: Your company spent $5,000 on marketing and generated an additional $6,000 in profit before accounting for the campaign cost. The net gain is $1,000 on a $5,000 investment, so the ROI is $1,000 / $5,000 = 20%.

 

11. Payback Period = Investment Cost / Profit per Year

 

Payback period is how long it takes a company to recoup the money it spent on an investment, usually measured in years.

 

Example: Your company invested $5,000 in redesigning its shirts and expects annual profit to rise by $1,000 going forward. The payback period is $5,000 / $1,000 = 5 years.

 

What Are the Operations Formulas for Case Interviews?

 

Operations formulas measure how much a company produces and how efficiently it uses its capacity. They show up in cases about factories, manufacturing, and service throughput.

 

12. Output = Rate x Time

 

Output is the total amount produced, calculated by multiplying the rate of production by the amount of time spent producing.

 

Example: The machine your company uses produces 5 shirts per hour. If it runs for 12 hours, it will produce 60 shirts.

 

13. Utilization = Output / Maximum Output

 

Utilization shows how much a factory or machine is being used relative to its maximum possible output. A low utilization rate points to wasted capacity.

 

Example: The machine can produce 5 shirts per hour, so its maximum in a 24-hour day is 120 shirts. If it is only producing 60 shirts per day, it is at 60 / 120 = 50% utilization.

 

What Are the Market Share Formulas for Case Interviews?

 

Market share formulas measure how strong a company's position is within its market. They are common in growth, market entry, and competitive cases.

 

14. Market Share = Company Revenue in the Market / Total Market Revenue

 

Market share is the percentage of total market sales a company holds. It ranges from 0%, meaning no presence, to 100%, meaning complete dominance.

 

Example: Your company sells shirts and generates $100M in annual revenue. The shirt market is $500M. Your market share is $100M / $500M = 20%.

 

15. Relative Market Share = Company Market Share / Largest Competitor's Market Share

 

Relative market share compares a company's market share to its largest competitor's. It measures how strong a company is relative to the market leader. If the company is the leader, it measures the size of its lead over the next player.

 

You can use revenue instead of market share in both the numerator and denominator and get the same answer.

 

Example: Your company has a 20% market share and your largest competitor has 50%. Your relative market share is 20% / 50% = 0.4.

 

Example 2: Your company is the leader with a 50% share and your largest competitor has 25%. Your relative market share is 50% / 25% = 2.

 

What Are the Customer and Pricing Formulas for Case Interviews?

 

Customer and pricing formulas come up in growth and subscription business cases. They help you judge whether a company makes more from a customer than it spends to acquire them.

 

16. Customer Lifetime Value = Average Purchase Value x Purchases per Year x Customer Lifespan

 

Customer lifetime value, or CLV, estimates the total revenue a single customer brings in over the full length of their relationship with the company. It matters most for subscription and recurring revenue businesses.

 

Example: A gym charges $50 per month and the average member stays for 2 years. The CLV is $50 x 12 x 2 = $1,200.

 

17. Customer Acquisition Cost = Total Sales and Marketing Spend / New Customers Acquired

 

Customer acquisition cost, or CAC, is how much a company spends to win one new customer. A healthy business keeps CAC well below CLV.

 

Example: A startup spends $100,000 on sales and marketing in a year and acquires 2,500 customers. Its CAC is $100,000 / 2,500 = $40 per customer.

 

What Are the Accounting, Finance, and Economics Formulas for Case Interviews?

 

These formulas are much less common than the ones above. You likely will not need them, since they require more technical knowledge of accounting, finance, and economics.

 

Still, you should be familiar with them in the small chance one of these concepts shows up in your case.

 

18. Gross Profit = Sales minus Cost of Goods Sold

 

Gross profit is how much a company makes from selling its product after the direct costs of making and selling it, often called the cost of goods sold.

 

Compared to the simple profit formula, gross profit is always higher because it does not account for all of the costs of the business.

 

Example: Your company sold $20,000 of shirts last year, and the cost to produce them was $5,000. Gross profit is $20,000 minus $5,000 = $15,000.

 

19. Operating Profit = Gross Profit minus Operating Expenses minus Depreciation minus Amortization

 

Operating profit takes gross profit and subtracts operating expenses along with depreciation and amortization.

 

Operating expenses include rent, utilities, maintenance, advertising, insurance, and wages, so operating profit is always less than gross profit.

 

Depreciation spreads a physical asset's cost over its useful life. A $10,000 machine expected to last 5 years can be counted as $2,000 per year rather than $10,000 in year one.

 

Amortization is the same idea applied to intangible assets. A $10,000 patent expected to last 20 years can be counted as $500 per year.

 

Example: You sold $20,000 of shirts. Cost of goods is $5,000, operating expenses are $10,000, depreciation is $2,000, and amortization is $500. Operating profit is $20,000 minus $5,000 minus $10,000 minus $2,000 minus $500 = $2,500.

 

20. Gross Profit Margin = Gross Profit / Revenue

 

This is the profit margin formula using gross profit. It measures how much a company keeps from selling its products after cost of goods sold.

 

Example: Your company has $15,000 in gross profit on $20,000 of revenue. The gross profit margin is $15,000 / $20,000 = 75%.

 

21. Operating Profit Margin = Operating Profit / Revenue

 

This is the profit margin formula using operating profit. It measures how much a company keeps after cost of goods sold, operating expenses, depreciation, and amortization.

 

Example: Your company has $2,500 in operating profit on $20,000 of revenue. The operating profit margin is $2,500 / $20,000 = 12.5%.

 

22. EBITDA = Operating Profit + Depreciation + Amortization

 

EBITDA stands for earnings before interest, taxes, depreciation, and amortization. It is used to estimate the cash a company has generated in a period. You start with operating profit and add back depreciation and amortization.

 

Example: Your company has $2,500 in operating profit, with $2,000 in depreciation and $500 in amortization. EBITDA is $2,500 + $2,000 + $500 = $5,000.

 

23. CAGR = (Ending Value / Beginning Value)^(1 / Number of Years) minus 1

 

CAGR stands for compound annual growth rate. It measures how quickly something grows year after year on average. Note that calculating a full CAGR by hand rarely comes up in interviews.

 

Example: Your company generates $144M in revenue today and generated $100M two years ago. The CAGR is ($144M / $100M)^(1/2) minus 1 = 20%. The company grew 20% per year for two years.

 

24. Rule of 72

 

The Rule of 72 is a shortcut to estimate how long it takes a company or investment to double in size. Divide 72 by the annual growth rate to get the number of years.

 

Example: Your company is growing at 9% per year. By the Rule of 72, it would take 72 / 9 = 8 years to double in size.

 

25. NPV = Cash Flow / (1 + Discount Rate)^(Number of Years)

 

NPV stands for net present value. It measures how much future cash flow is worth today.

 

Receiving $1,000 now is not the same as receiving $1,000 in five years. If you had it now, you could invest it and grow it. Net present value accounts for that.

 

Cash flow is the money you expect in the future, the number of years is how far out you receive it, and the discount rate is the return you could earn by investing instead.

 

Example: You expect $1,000 in five years and could earn 8% annually in the market. The net present value is $1,000 / (1.08)^5 = $680.58. Receiving $680.58 today is worth the same as $1,000 in five years.

 

26. Perpetuity: Present Value = Cash Flow / Discount Rate

 

A perpetuity is a fixed payment that lasts forever. The present value of a perpetuity equals the cash flow of each payment divided by the discount rate.

 

Example: You expect $1,000 per year forever and could earn 8% annually. The present value is $1,000 / 0.08 = $12,500.

 

27. Return on Equity and Return on Assets

 

Return on equity, or ROE, measures how effectively a company uses shareholder money to create profit. You calculate it as Profit / Shareholder Equity, where shareholder equity is total assets minus total liabilities.

 

Example: Your company's profit is $100M and shareholder equity is $1B. ROE is $100M / $1B = 10%.

 

Return on assets, or ROA, measures how profitable a company is relative to its total assets. You calculate it as Profit / Total Assets.

 

Example: Your company's profit is $100M and total assets are $400M. ROA is $100M / $400M = 25%.

 

Two related economics concepts are price elasticity of demand, which is the percent change in quantity divided by the percent change in price, and cross elasticity of demand, which is the percent change in quantity of one good divided by the percent change in price of another. A negative cross elasticity means two goods are complements, while a positive one means they are substitutes.

 

How Do You Apply Case Interview Formulas in a Live Case?

 

Knowing the formulas is only half the job. What separates strong candidates is applying the right formula at the right moment and explaining what the answer means for the business. Here is how the formulas show up across the most common case types.

 

How Do Formulas Show Up in a Profitability Case?

 

Start with Profit = Revenue minus Costs, then break each side down. Use Revenue = Quantity x Price to test whether the problem is volume or price. Use Costs = Variable + Fixed to test whether variable or fixed costs are rising.

 

Once you isolate the driver, profit margin and contribution margin help you quantify the impact and judge how serious it is.

 

How Do Formulas Show Up in a Market Entry or Growth Case?

 

Use the market sizing logic to estimate how big the opportunity is, then use market share and growth rate to estimate how much of it the company can capture and how fast it is expanding.

 

Breakeven quantity then tells you how many units the company needs to sell to justify the entry cost.

 

How Do Formulas Show Up in an Investment or Pricing Case?

 

For an investment decision, ROI and payback period tell you whether the return justifies the cost. For pricing, contribution margin and breakeven show how a price change flows through to profit and how many sales you need at the new price.

 

If you want a structured way to learn each of these case types with practice drills, my case interview course walks you through every formula and calculation type in as little as 7 days.

 

What Are the Most Common Case Interview Math Mistakes?

 

Even strong candidates lose points on case math, and it is rarely because the math is hard. It is because of avoidable mistakes under time pressure. Here are the most common ones and how to avoid them.

 

1. Choosing the wrong formula. Match the formula to the question. If the interviewer asks how fast something is growing, use growth rate or CAGR, not a one-time percentage.
    
2. Mixing up fixed and variable costs. Misclassifying a cost throws off your breakeven and margin answers. The quick test: if producing one more unit raises the cost, it is variable.
   
   
3. Forgetting to sense check. Ask whether your answer is too big or too small before you say it out loud. Missing or extra zeros are the most common arithmetic error.
   
   
4. Ignoring units. Annual versus monthly, millions versus thousands. Confirm the units before you calculate so you do not deliver an answer that is off by a factor of 12 or 1,000.
   
   
5. Calculating silently. If you do the math in your head without talking, the interviewer cannot follow you and cannot help if you slip. State the formula, then walk through the steps out loud.
   
   
6. Stopping at the number. A number with no interpretation adds no value. Always say what the answer means for the client and what you would do about it.

 

What Are the Best Tips for Case Interview Formulas?

 

Use these tips to make the formulas work for you under interview pressure.

 

Tip #1: Memorize the core formulas cold.

You should be able to recall profit, revenue, cost, margin, contribution margin, breakeven, and growth rate without thinking. The mental space you save goes toward solving the actual problem.

 

Tip #2: Ask permission to round.

Most interviewers will let you round numbers to make the math easier. Multiplying 300 million by 50% is far faster than 311 million by 43%, and the answer is close enough.

 

Tip #3: Write the formula before plugging in numbers.

Saying the formula out loud and writing it down lets the interviewer follow your logic and step in if you are headed the wrong way.

 

Tip #4: Practice mental math daily.

Calculators are not allowed, so build speed with quick daily drills. Calculating tips, splitting bills, and estimating discounts all count as practice.

 

Tip #5: Always connect the number to the business.

After you solve, explain what the answer means. A 5% margin is not just a number, it is a sign the company is underperforming and needs to act.

 

Frequently Asked Questions

 

What are the most important case interview formulas?

 

The most important formulas are profit equals revenue minus costs, revenue equals quantity times price, costs equal variable plus fixed costs, profit margin, contribution margin, breakeven quantity, and growth rate. These appear in the large majority of cases, so learn them first.

 

Do you need to memorize case interview formulas?

 

Yes, you should memorize the core formulas so you can apply them instantly during a live case. Calculators are not allowed, and pausing to remember a formula wastes time and breaks your communication with the interviewer. The accounting and finance formulas are worth recognizing but rarely need to be memorized.

 

What is the profit formula for case interviews?

 

The profit formula is Profit = Revenue minus Costs. Revenue equals quantity times price, and costs equal variable costs plus fixed costs. From these three equations you can build a framework for almost any profitability case.

 

What is the breakeven formula in a case interview?

 

The breakeven formula is Breakeven Quantity = Fixed Costs / Contribution Margin, where contribution margin is price minus variable cost. It tells you how many units a company must sell to cover all of its costs. Before using it, confirm that price is greater than variable cost, otherwise breakeven is impossible.

 

How do you calculate growth rate in a case interview?

 

Growth rate equals the new value minus the old value, divided by the old value. For example, going from $100M to $120M is a growth rate of $20M / $100M = 20%. A negative result means the figure declined over the period.

 

Is the math in case interviews hard?

 

No, the math itself is just arithmetic, percentages, and a handful of business formulas. The challenge is doing it quickly and accurately under time pressure without a calculator. With consistent practice, anyone can master case interview math.

 

How many formulas do you really need for a case interview?

 

You can solve the vast majority of cases with about a dozen core formulas covering profit, revenue, cost, margin, breakeven, growth, market share, and return on investment. The remaining accounting and finance formulas are useful to recognize but appear only rarely.

 

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