McKinsey's interview process is known for being rigorous and structured. Understanding how they specifically test math will help you prepare more effectively.
How McKinsey Uses Math in Cases
McKinsey cases tend to be interviewer-led, meaning the interviewer guides you through specific questions rather than letting you drive completely.
What this means for math:
- Questions are often precise: "What's the breakeven volume?"
- Less open-ended estimation, more specific calculations
- Exhibits and charts are common
- Speed matters—you'll move through several questions
Typical McKinsey-Style Math Questions
Chart-Based Calculations
"Looking at this exhibit, what was the compound annual growth rate of segment A?"
Quick Breakeven
"If fixed costs are $2M and contribution margin is $40/unit, how many units to break even?"
Percentage Comparisons
"Product X has 25% margin on $80M revenue. Product Y has 30% margin on $60M revenue. Which contributes more profit?"
Data Synthesis
"Based on these three data points, what's the total addressable market?"
How Fast You Really Need to Be
Based on typical McKinsey case pacing:
| Calculation Type | Target Time |
|---|---|
| Simple percentage | 10-15 seconds |
| Two-step calculation | 20-30 seconds |
| Chart reading + calc | 45-60 seconds |
| Complex multi-step | 60-90 seconds |
If you're consistently slower, you won't finish the case comfortably.
7-Day McKinsey Math Training Plan
Day 1-2: Foundation
- 3 × Mental Math Sprints (medium difficulty)
- Review percentage and fraction conversions
- Practice: 50 basic calculations
Day 3-4: Business Formulas
- Memorize breakeven, margin, growth formulas
- 2 × Case Math Drills focusing on profitability
- Practice explaining calculations out loud
Day 5-6: Chart Interpretation
- Work through 10 chart-based problems
- Practice extracting data quickly
- Time yourself on each
Day 7: Integration
- Full practice case with math-heavy components
- Review any weak areas
- Final Mental Math Sprint for confidence
Example McKinsey-Flavored Questions
These represent typical patterns, not actual McKinsey questions.
Q1: "A company has $500M revenue growing at 8% annually. Costs are $450M growing at 10% annually. In how many years will they become unprofitable?"
Q2: "Looking at this chart of regional sales, which region showed the highest absolute growth? The highest percentage growth?"
Q3: "The client can invest in Project A (ROI 18%, 2-year payback) or Project B (ROI 25%, 4-year payback). What factors should inform their decision?"
Using Case Math Practice for McKinsey
Recommended setup:
- Mental Math Sprint — Set to "Hard" difficulty, practice until you consistently score 15+ questions
- Case Math Drills — Focus on "Profitability" and "Growth" topics
- Daily minimum — 15 minutes of focused math practice
Key Takeaways
- McKinsey math is fast-paced and specific
- Chart interpretation is crucial
- Practice verbalizing your calculations
- Speed comes from daily practice, not cramming
- Accuracy > speed, but you need both
Ready to practice? Start a Mental Math Sprint →