Market sizing questions, with worked examples

Q: Estimate how many cups of coffee are sold in the U.S. each day.

Clear top-down or bottom-up structure. U.S. population about 330M, share who drink coffee, cups per drinker. States assumptions and rounds cleanly. Sanity check, answer roughly 300–500M cups a day.

Q: Estimate how many smartphones are sold in the U.S. each year.

Population about 330M, share with smartphones. Replacement cycle of about 2–3 years. Clear math with rounded numbers. Sanity check, lands roughly in the 100–150M range.

Q: Estimate the size of the U.S. college textbook market.

Students × courses × spending per course. States assumptions (about 19M students, rentals and used books). Reasonable final range. Sanity check against total spending per student.

Q: Estimate the annual revenue of a single Starbucks store.

Customers per hour by time of day. Average ticket size. Hours open × days a year. Sanity check: company-run stores average roughly $2–2.5M a year.

Market sizing questions ask you to estimate a number you can't look up, like how many cups of coffee Americans drink a day. Interviewers grade the process, not the exact answer.

Pick top-down (start from a big number like population and narrow it) or bottom-up (start from one store or customer and scale up). Say your assumptions out loud, round to easy numbers, and sanity-check at the end. Handy anchors: about 330 million people in the U.S. and about 130 million households.

Market sizing practice

Basic

Estimate how many cups of coffee are sold in the U.S. each day.

A strong answer covers

Clear top-down or bottom-up structure
U.S. population about 330M, share who drink coffee, cups per drinker
States assumptions and rounds cleanly
Sanity check, answer roughly 300–500M cups a day

Basic

Estimate how many smartphones are sold in the U.S. each year.

A strong answer covers

Population about 330M, share with smartphones
Replacement cycle of about 2–3 years
Clear math with rounded numbers
Sanity check, lands roughly in the 100–150M range

Intermediate

How many gas stations are there in the United States?

A strong answer covers

Structured approach (cars, fill-ups, station capacity or population per station)
States assumptions clearly
Lands on a reasonable number (the industry estimate is about 150,000 fueling sites)
Sanity-checks the result

Intermediate

How many tennis balls are sold in the U.S. each year?

A strong answer covers

Segments buyers (casual players, regular players, clubs, pros)
Players × balls per year by segment
Clear math with rounded numbers
Sanity check against something known

Advanced

Estimate the size of the U.S. college textbook market.

A strong answer covers

Students × courses × spending per course
States assumptions (about 19M students, rentals and used books)
Reasonable final range
Sanity check against total spending per student

Advanced

Estimate the annual revenue of a single Starbucks store.

A strong answer covers

Customers per hour by time of day
Average ticket size
Hours open × days a year
Sanity check: company-run stores average roughly $2–2.5M a year

Quick quiz (10 questions)

Starting from the U.S. population and narrowing down is a:

Bottom-up estimate
Top-down estimate ✓
DCF
Regression

Top-down starts with a big number and applies filters.

Why round numbers in market sizing?

Interviewers want exact answers
To keep the math fast and easy to follow ✓
Rounding is always more accurate
To hide your assumptions

Clean numbers keep you quick and let the interviewer follow your logic.

330M people, half drink coffee, 1 cup a day each. About how many cups a day?

16.5 million
165 million ✓
1.65 billion
330 million

330M × 50% × 1 = 165M cups a day.

Starting from one store and scaling up is:

Top-down
Bottom-up ✓
A DCF
A regression

Bottom-up builds from a unit.

U.S. population for market sizing is usually rounded to:

330 million ✓
33 million
3.3 billion
1 billion

About 330 million keeps math easy.

330M people, 40% drink soda, 1 can per day. Cans per day:

13.2M
1.32B
330M
132M ✓

330M × 40% = 132M.

About how many U.S. households are there for quick estimates?

13 million
About 130 million ✓
1.3 billion
30 million

Roughly 130 million households, about 2.5 people each.

In a market sizing question, why say your assumptions out loud?

Because interviewers grade you on how many assumptions you can list
Because it's required by law
To hide your errors from them
So the interviewer can follow and correct them ✓

Transparent logic matters more than the exact number.

Estimate yearly gym members if 330M people and 15% have a membership:

5M
50M ✓
500M
15M

330 × 15% ≈ 50M.

In case math, why round 365 days to about 360 or 350?

A year has exactly 360 days
Easier mental math with small accuracy loss ✓
Because rounding is required
Because 360 is more accurate

Round numbers speed things up.

Reading isn't practice. Answer these out loud, get scored, and track your progress for free.

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Market sizing questions, with worked examples

Market sizing practice

Estimate how many cups of coffee are sold in the U.S. each day.

Estimate how many smartphones are sold in the U.S. each year.

How many gas stations are there in the United States?

How many tennis balls are sold in the U.S. each year?

Estimate the size of the U.S. college textbook market.

Estimate the annual revenue of a single Starbucks store.

Quick quiz (10 questions)

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