Case math is not a quant interview. It is whether you can set the equation up, keep units attached, and say what the number means before the interviewer asks.
Last full pass: 24 August 2026.
Pick the leak
| Leak | Guide | Drill |
|---|---|---|
| You cannot size a market without a template panic | Market sizing step by step · market sizing questions · guesstimates | /drills/market-sizing |
| Arithmetic is slow or sloppy | Mental math · shortcuts · math practice | /drills/quick-math |
| You forget which formula you need | Consulting math formulas | Formula sheet, then a timed case |
| Breakeven / contribution | Breakeven | /tools/breakeven-calculator |
| Payback / ROI | ROI and payback | Work the units before the percentage |
Calculators (after you can do it by hand)
A calculator is a check, not a crutch. In the room you have a pen, a rounding convention, and an interviewer who will ask what happens if volume is 10% worse.
The rule that saves most candidates
Set the equation out loud before you punch numbers. “Revenue is price × volume; I will use $40 and 2.1 million units” scores even if the multiply slips. A silent right number with no setup does not.
When the math is clean, go back to frameworks or sit a full case. Math without a so-what is a spreadsheet, not a recommendation.