This case interview math formulas cheat sheet gives you the essential equations you'll see in consulting case interviews at McKinsey, BCG and Bain. Print it, save it, and review it daily until these formulas become second nature.
Why a Cheat Sheet Matters
Most candidates lose time remembering formulas, not doing actual thinking. When you have the formulas memorized cold, you can focus on what really matters: structuring the problem, making assumptions, and communicating your insights.
The difference between a good candidate and a great one often comes down to speed and confidence with basic math. This cheat sheet gets you there.
Must-Know Case Math Formulas
These formulas appear in 80%+ of case interviews. Master them first.
| Formula | Plain English |
|---|---|
| Profit = Revenue - Costs | What's left after paying all expenses |
| Revenue = Price × Quantity | How much money comes in |
| Gross Margin = (Revenue - COGS) / Revenue | Profit % before overhead |
| Operating Margin = EBIT / Revenue | Profit % from core operations |
| Breakeven Units = Fixed Costs / (Price - VC) | Units needed to cover all costs |
| Contribution Margin = Price - Variable Cost | Profit per unit before fixed costs |
| Growth Rate = (New - Old) / Old × 100% | How much something increased |
| ROI = (Gain - Cost) / Cost × 100% | Return on investment |
| Payback Period = Investment / Annual Cash Flow | Years to recover investment |
Optional but Nice-to-Have Formulas
These appear less frequently but can impress interviewers:
ROA (Return on Assets)
- Formula: Net Income / Total Assets
- When it appears: Asset-heavy industries (manufacturing, airlines)
ROE (Return on Equity)
- Formula: Net Income / Shareholders' Equity
- When it appears: Financial services, investor discussions
Operating Leverage
- Formula: % Change in Operating Income / % Change in Revenue
- When it appears: Cost structure analysis
NPV Intuition
- Concept: Future cash flows discounted to present value
- When it appears: Investment decisions (rarely need full calculation)
Annotated Worked Examples
Example 1: Profitability Breakdown
A retail company has revenue of $100M, COGS of $60M, and operating expenses of $25M.
Step 1: Gross Profit = $100M - $60M = $40M
Step 2: Gross Margin = $40M / $100M = 40%
Step 3: Operating Profit = $40M - $25M = $15M
Step 4: Operating Margin = $15M / $100M = 15%
Sanity check: Margins are positive and reasonable for retail ✓
Example 2: Breakeven Units
A SaaS company has fixed costs of $500K/month. Each subscription costs $50/month with variable costs of $10/user.
Step 1: Contribution Margin = $50 - $10 = $40/user
Step 2: Breakeven = $500,000 / $40 = 12,500 users
Sanity check: ~12K users for a SaaS seems achievable ✓
Example 3: ROI Decision
Marketing wants to spend $200K on a campaign expected to generate $280K in incremental revenue.
Step 1: Gain = $280K - $200K = $80K
Step 2: ROI = $80K / $200K = 40%
Decision: 40% ROI is typically above hurdle rate—recommend proceeding ✓
Example 4: CAGR Calculation
Revenue grew from $10M to $16M over 4 years.
Step 1: Growth multiple = 16/10 = 1.6x
Step 2: CAGR ≈ (1.6)^(1/4) - 1 ≈ 12.5%
Quick check using Rule of 72: At 12%, doubles in ~6 years. 4 years = 60% growth. $10M × 1.6 = $16M ✓
How to Use This Cheat Sheet in Prep
Routine 1: Daily Review
Read through the formulas once per day before your practice session. Takes 5 minutes, pays dividends.
Routine 2: Write from Memory
Before each practice session, write 3 random formulas from memory. Check against this sheet. Fix any gaps.
Routine 3: Translate to Words
Pick one formula and explain it in plain English as if to a non-business friend. This builds intuition.
Download: Printable PDF & Mobile Wallpaper
Coming soon: Downloadable PDF version optimized for printing and a mobile wallpaper version (1080x1920) you can set as your lock screen.
For now, bookmark this page or save it to your notes app.
Next Steps: Practice the Formulas
Knowing formulas is step one. Applying them under pressure is step two.
- Mental Math Sprint — Build speed with timed drills
- Case Math Drills — Practice business scenarios
- 14-Day Study Plan — Structured preparation path
Master the formulas, ace the math, land the offer.