Guide · Market sizing
20 market sizing questions with worked answers
TL;DR
Market sizing is graded on structure, not on the final number. Pick top-down or bottom-up, state your assumptions, do the math out loud, and end with a single defensible figure. The 20 worked examples below show the structure that consultants expect.
Last updated: May 16, 2026. Written by the CaseXcel team.
Top-down vs bottom-up
Top-down starts from a known total (population, GDP, total fleet) and narrows by ratios. Faster and cleaner for most case interview prompts. Use top-down by default.
Bottom-up starts from a unit (one customer, one item, one transaction) and multiplies up. Useful when the unit economics are easier to anchor than the top number — for example, "how big is the global solar panel market" is easier to size from gigawatts × price than from population.
If you are between the two, pick top-down. The interviewer is more likely to follow along.
20 worked sizing questions
How many dentists practice in Germany?
Structure
- Germany population: ~84M
- Assume 1 dentist per ~1,200 people (developed-market norm)
- Therefore: 84M ÷ 1,200
Math
84,000,000 ÷ 1,200 ≈ 70,000
Answer
~70,000 dentists in Germany (actual: ~75,000).
How many cups of coffee are sold in NYC each day?
Structure
- NYC population: ~8.4M
- Assume 60% drink coffee daily, average 1.5 cups
- 8.4M × 60% × 1.5 = ~7.5M cups
- Add ~10% for commuters and tourists
Math
8.4M × 0.6 × 1.5 ≈ 7.5M; +10% ≈ 8.3M
Answer
~8 million cups of coffee per day in NYC.
What is the annual revenue of all yoga studios in the US?
Structure
- US population: ~330M
- Yoga practitioners: ~10% (33M)
- Studio-going practitioners: ~40% (13M)
- Avg spend: $80/month × 12 = $960/year
Math
13M × $960 ≈ $12.5B
Answer
~$12 billion in annual US yoga-studio revenue.
How many airline passengers fly between London and New York each year?
Structure
- ~30 daily flights each way (large hubs, year-round demand)
- Avg aircraft: 250 seats, 85% load factor → 212 passengers per flight
- 30 × 2 directions × 365 days × 212 passengers
Math
60 × 365 × 212 ≈ 4.6M
Answer
~4-5 million passengers per year on the LHR/JFK corridor.
How big is the global market for headphones?
Structure
- Global smartphone users: ~5B
- Assume 70% own headphones, replace every 3 years
- Avg ASP $40
Math
5B × 0.7 ÷ 3 × $40 ≈ $47B
Answer
~$45-50 billion globally per year.
How many EV charging stations does the UK need by 2030?
Structure
- UK fleet ~32M vehicles, ~50% EVs by 2030 → 16M EVs
- Assume 1 public charger per 30 EVs (industry benchmark)
Math
16M ÷ 30 ≈ 530,000
Answer
~500,000 public chargers required by 2030.
What is the annual market for school uniforms in the UK?
Structure
- School-age children (5-16): ~8M
- Assume 60% wear uniforms (state + private)
- Avg annual spend per student: £80
Math
8M × 0.6 × £80 ≈ £380M
Answer
~£350-400 million per year.
How many gym memberships are active in France?
Structure
- France population: ~68M
- Adults (18-65): ~60% → 41M
- Gym penetration: 10%
Math
41M × 0.10 ≈ 4.1M
Answer
~4 million active gym memberships in France.
How many slices of pizza are sold in Italy each year?
Structure
- Avg Italian consumes ~7.5 kg pizza/year
- Assume slice = 150g
- Slices per person: 50
- Italy population: ~59M
Math
59M × 50 ≈ 3B
Answer
~3 billion slices of pizza per year.
How big is the US private-tutoring market?
Structure
- K-12 students in US: ~55M
- Households using tutoring: ~20% → 11M students
- Avg annual spend: $1,500
Math
11M × $1,500 ≈ $16B
Answer
~$15-17 billion per year.
How many AirPods are sold globally per year?
Structure
- Apple active iPhone users: ~1.4B
- AirPods penetration ~30%, replace every 3 years
Math
1.4B × 0.30 ÷ 3 ≈ 140M
Answer
~130-150M units per year globally.
What is the annual revenue of all NYC yellow cabs?
Structure
- 13,000 medallion cabs
- Avg trip: $18, ~25 trips per shift
- 2 shifts/day, 350 days/year
Math
13,000 × $18 × 25 × 2 × 350 ≈ $4.1B
Answer
~$4 billion per year (pre-Uber baseline; current is materially lower).
How many lightbulbs are sold in the US each year?
Structure
- US households: ~130M
- Avg bulbs per home: 40
- LED lifespan ~10 years → 1/10 replaced per year
- Plus commercial: assume 30% on top of residential
Math
130M × 40 ÷ 10 × 1.3 ≈ 680M
Answer
~600-700 million bulbs per year in the US.
How big is the streaming-music market in Brazil?
Structure
- Brazil population: ~215M
- Streaming subscribers: ~25% of adults (~40M)
- Avg ARPU: $4/month × 12
Math
40M × $48 ≈ $1.9B
Answer
~$1.5-2 billion per year in Brazil.
How many haircuts happen in London per month?
Structure
- London adults: ~7M
- Haircuts per adult per year: ~8 (avg of men ~12, women ~4 + dyes)
Math
7M × 8 ÷ 12 ≈ 4.7M
Answer
~4-5 million haircuts per month in London.
How many SaaS products does a typical US enterprise use?
Structure
- Department breakdown: 5-10 SaaS each in sales, finance, HR, IT, eng, ops
- Average: ~7 per function × ~8 functions
Math
7 × 8 ≈ 56
Answer
~50-100 SaaS products per enterprise (consistent with industry surveys).
How big is the European luxury watch market?
Structure
- EU + UK affluent households: ~30M
- Annual luxury-watch buyers: ~3% → 900K buyers
- Avg purchase: €5,000
Math
900K × €5,000 ≈ €4.5B
Answer
~€4-5 billion per year in Europe.
What is the annual market size for baby formula in China?
Structure
- Births per year in China: ~9M
- Assume 60% formula-fed for ~12 months
- Avg annual spend per baby: $1,200
Math
9M × 0.6 × $1,200 ≈ $6.5B
Answer
~$6-8 billion per year in China.
How many uber rides happen in Paris per day?
Structure
- Paris adult population: ~9M (metro)
- Adults using rideshare weekly: ~10% → 900K
- Avg 2 rides per weekly user
Math
900K × 2 ÷ 7 ≈ 260K
Answer
~250-300K rides per day in Paris.
How big is the global market for solar panels?
Structure
- Global PV installs per year: ~400 GW
- Avg price ~$0.25 per watt
Math
400B watts × $0.25 ≈ $100B
Answer
~$100 billion per year globally.
Common mistakes
- Skipping the structure and jumping straight to a number. The structure is the answer.
- Stating assumptions silently. Always say "I'll assume X is Y" out loud.
- Refusing to commit to a number at the end. A defensible $4 billion beats "somewhere between $1B and $10B."
- Picking population brackets too narrow ("adults 25-34") when wider would do.
- Doing the math wrong because you did not round. Round aggressively in your head; precision is not the point.
Drill market sizing in 5 minutes a day
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