Why You Need This Cheat Sheet
Market sizing questions appear in almost every consulting interview. Having key numbers memorized lets you focus on structure and logic rather than guessing basic facts.
Bookmark this page and review it before your interview.
Population Numbers (Memorize These)
United States
| Metric | Value |
|---|---|
| Total Population | 330 million |
| Households | 130 million |
| Average Household Size | 2.5 people |
| Working Age Adults (18-65) | 200 million |
| Workers (employed) | 160 million |
| Births per Year | 4 million |
| Deaths per Year | 3 million |
Major Countries
| Country | Population |
|---|---|
| World | 8 billion |
| China | 1.4 billion |
| India | 1.4 billion |
| European Union | 450 million |
| Germany | 84 million |
| UK | 67 million |
| France | 68 million |
| Japan | 125 million |
| Brazil | 215 million |
US Demographics
| Age Group | Population |
|---|---|
| Children (0-17) | 75 million |
| Young Adults (18-34) | 70 million |
| Middle Age (35-54) | 85 million |
| Older Adults (55+) | 100 million |
Economic Numbers
US Income & Spending
| Metric | Value |
|---|---|
| Median Household Income | $75,000 |
| Average Household Income | $100,000 |
| Median Individual Income | $45,000 |
| Consumer Spending per Capita | $50,000/year |
| US GDP | $25 trillion |
Common Prices (US)
| Item | Price |
|---|---|
| Gallon of Gas | $3.50 |
| Coffee (café) | $5 |
| Movie Ticket | $15 |
| New Car (average) | $50,000 |
| Used Car (average) | $25,000 |
| Average Home | $400,000 |
| Rent (1BR national avg) | $1,500/month |
| Smartphone | $800 |
| Annual Healthcare Spending | $4,500/person |
Business Benchmarks
Typical Margins by Industry
| Industry | Gross Margin | Operating Margin |
|---|---|---|
| Software/SaaS | 70-85% | 20-30% |
| Retail (grocery) | 25-30% | 2-4% |
| Retail (fashion) | 50-60% | 8-12% |
| Manufacturing | 30-40% | 8-15% |
| Restaurants | 60-70% | 5-10% |
| Airlines | 20-30% | 5-10% |
| Pharma | 65-80% | 20-30% |
| Financial Services | N/A | 25-35% |
Conversion & Usage Rates
| Metric | Typical Range |
|---|---|
| E-commerce conversion | 2-3% |
| SaaS trial-to-paid | 10-25% |
| Email open rate | 15-25% |
| App download-to-active | 20-30% |
| Customer churn (SaaS) | 5-10% annually |
| Customer churn (telecom) | 15-25% annually |
Time-Based Numbers
Daily Life (Per Person)
| Activity | Time/Frequency |
|---|---|
| Hours awake | 16 hours |
| Meals | 3 per day |
| Showers | 1 per day |
| Phone screen time | 4-5 hours |
| TV watching | 4 hours |
| Commute time | 1 hour |
Annual Timeframes
| Metric | Value |
|---|---|
| Hours in a year | 8,760 (≈9,000) |
| Working hours/year | 2,000 |
| School days/year | 180 |
| Weekend days/year | 104 |
| Average vacation days (US) | 10-15 |
Market Sizing Frameworks
Top-Down Approach
Formula: Total Population → Segment → Usage Rate → Frequency → Price
Example: US Toothpaste Market
- US Population: 330M
- People who brush teeth: 95% = 315M
- Tubes per person per year: 4
- Price per tube: $4
- Market = 315M × 4 × $4 = $5B
Bottom-Up Approach
Formula: # of Locations × Output per Location × Price
Example: Coffee Shop Revenue in NYC
- Coffee shops in NYC: ~3,000
- Customers per shop per day: 200
- Average ticket: $6
- Days per year: 350
- Market = 3,000 × 200 × $6 × 350 = $1.26B
Sanity Checks
Per Capita Check
Divide your market size by population. Does the per-person number make sense?
- $50B market / 330M people = $150/person/year
- Ask: Would the average American spend $150/year on this?
Comparison Check
How does your estimate compare to known markets?
- US auto market: ~$500B
- US grocery market: ~$800B
- US healthcare: ~$4 trillion
- US housing: ~$50 trillion (total value)
Growth Check
- Mature markets: 2-5% growth
- Growing markets: 10-15% growth
- High-growth tech: 20-40% growth
- If your numbers imply 50% growth, double-check!
Practice These Estimations
Try these with a 3-minute timer:
- Diapers sold in the US annually
- Pizza delivery market in NYC
- Electric vehicle charging stations needed by 2030
- Revenue of a single Starbucks location
- Annual spend on dog food in Germany
Quick Reference Card
Must-Know Numbers:
- US Population: 330M
- US Households: 130M
- US GDP: $25T
- World Population: 8B
- Hours/year: 9,000
- Working hours/year: 2,000
Percentage Quick Math:
- 10% = ÷10
- 25% = ÷4
- 33% = ÷3
- 50% = ÷2
- 75% = ×3÷4
Sanity Check: Per capita should "feel right" for the average person.
Next Steps
Put these numbers to work:
- Mental Math Sprint — Practice calculations
- Brain Teasers — Estimation puzzles
- Complete Math Guide — All formulas
Bookmark this page. Review before every interview.
Market sizing also appears in finance interviews for valuation and deal analysis. For IB/PE-specific prep, see Finance Interview Prep.