Ten market sizing questions with the sizing path
Ten market sizing questions from consulting interviews, each with its chain of factors, every assumption labeled, the answer computed by script, and the check.
Updated October 28, 2026
| # | Question | Chain | About |
|---|---|---|---|
| 1 | How many coffee shops are there in the United States? | US population x share who buy coffee out at least weekly x cups out per person per week x weeks a year x shops per cup per year | 145,000 shops |
| 2 | How many passengers fly out of a large US hub airport in a year? | daily departures x seats per departure x load factor x days a year | 52.6M passengers |
| 3 | How much do US households spend on pet food a year? | US households x share with a dog or cat x average pets per pet household x dollars per pet per year | $59B |
| 4 | How many shared electric scooters does a city of 2 million need? | population x share who would ride at least weekly x rides per rider per week x weeks x scooters per ride per year | 13,000 scooters |
| 5 | What is the annual revenue of a 1,000-seat movie theater? | seats x showings a day x occupancy x days a year x revenue per ticket including concessions | $8.1M |
| 6 | How many delivery trucks does a national parcel carrier need? | parcels a day x share delivered by its own trucks x trucks per parcel per day | 107,000 trucks |
| 7 | How big is the US market for running shoes? | US population x share who run regularly x pairs a year x dollars a pair | $9.0B |
| 8 | How many hotel rooms does a city of 5 million need? | visitor nights a year x rooms per guest night x rooms per room-night per year | 61,000 rooms |
| 9 | How many ATMs are there in the United States? | US adults x share who use an ATM at least monthly x withdrawals per user per month x months x ATMs per withdrawal per year | 107,000 ATMs |
| 10 | What is the annual revenue of a single supermarket? | households within reach x share who shop there mainly x trips a week x weeks x dollars a trip | $37M |
How do these questions work?
Every market sizing question is a multiplication. The skill is choosing the factors so that each one is either a number you know roughly or an assumption you can defend in a sentence, then multiplying out loud with rounding at every step, then checking the result against a ratio. The EV charging walkthrough does one chain slowly; this page does ten quickly, so the pattern becomes visible.
Two chains fit most questions. Demand: people, the share who do the thing, how often, how much. Supply: units of capacity, how much each delivers, utilization. Say which you are using before you start. When the question is about a count of things (shops, trucks, ATMs), the chain usually ends by dividing demand by what one unit handles.
The ten, step by step
1. How many coffee shops are there in the United States?
| Step | Factor | Note | Running |
|---|---|---|---|
| US population | 335,000,000 | rounded public figure | 335.0M |
| share who buy coffee out at least weekly | 40% | assumption | 134.0M |
| cups out per person per week | 3 | assumption | 402.0M |
| weeks a year | 52 | 20904.0M | |
| shops per cup per year | 1 / 144,000 | assumption: 400 cups a shop a day, 360 days | 145,000 shops |
Answer: about 145,000 shops. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
2. How many passengers fly out of a large US hub airport in a year?
| Step | Factor | Note | Running |
|---|---|---|---|
| daily departures | 1,200 | assumption for a large hub | 1200 |
| seats per departure | 150 | assumption | 180,000 |
| load factor | 80% | assumption | 144,000 |
| days a year | 365 | 52.6M passengers |
Answer: about 52.6M passengers. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
3. How much do US households spend on pet food a year?
| Step | Factor | Note | Running |
|---|---|---|---|
| US households | 130,000,000 | rounded public figure | 130.0M |
| share with a dog or cat | 60% | assumption | 78.0M |
| average pets per pet household | 1.5 | assumption | 117.0M |
| dollars per pet per year | 500 | assumption | $59B |
Answer: about $59B. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
4. How many shared electric scooters does a city of 2 million need?
| Step | Factor | Note | Running |
|---|---|---|---|
| population | 2,000,000 | given | 2.0M |
| share who would ride at least weekly | 5% | assumption | 100,000 |
| rides per rider per week | 3 | assumption | 300,000 |
| weeks | 52 | 15.6M | |
| scooters per ride per year | 1 / 1,200 | assumption: 4 rides a scooter a day, 300 days | 13,000 scooters |
Answer: about 13,000 scooters. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
5. What is the annual revenue of a 1,000-seat movie theater?
| Step | Factor | Note | Running |
|---|---|---|---|
| seats | 1,000 | given | 1000 |
| showings a day | 5 | assumption | 5000 |
| occupancy | 30% | assumption, averaged over the week | 1500 |
| days a year | 360 | 540,000 | |
| revenue per ticket including concessions | 15 | assumption | $8.1M |
Answer: about $8.1M. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
6. How many delivery trucks does a national parcel carrier need?
| Step | Factor | Note | Running |
|---|---|---|---|
| parcels a day | 20,000,000 | assumption for a large US carrier | 20.0M |
| share delivered by its own trucks | 80% | assumption | 16.0M |
| trucks per parcel per day | 1 / 150 | assumption: 150 stops a truck a day | 107,000 trucks |
Answer: about 107,000 trucks. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
7. How big is the US market for running shoes?
| Step | Factor | Note | Running |
|---|---|---|---|
| US population | 335,000,000 | rounded public figure | 335.0M |
| share who run regularly | 15% | assumption | 50.3M |
| pairs a year | 1.5 | assumption | 75.4M |
| dollars a pair | 120 | assumption | $9.0B |
Answer: about $9.0B. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
8. How many hotel rooms does a city of 5 million need?
| Step | Factor | Note | Running |
|---|---|---|---|
| visitor nights a year | 25,000,000 | assumption: five inbound visitor nights per resident | 25.0M |
| rooms per guest night | 63% | assumption: 1.6 guests a room | 15.6M |
| rooms per room-night per year | 1 / 255 | assumption: 70% occupancy | 61,000 rooms |
Answer: about 61,000 rooms. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
9. How many ATMs are there in the United States?
| Step | Factor | Note | Running |
|---|---|---|---|
| US adults | 260,000,000 | rounded public figure | 260.0M |
| share who use an ATM at least monthly | 50% | assumption | 130.0M |
| withdrawals per user per month | 3 | assumption | 390.0M |
| months | 12 | 4680.0M | |
| ATMs per withdrawal per year | 1 / 43,800 | assumption: 120 withdrawals an ATM a day | 107,000 ATMs |
Answer: about 107,000 ATMs. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
10. What is the annual revenue of a single supermarket?
| Step | Factor | Note | Running |
|---|---|---|---|
| households within reach | 20,000 | assumption for a suburban store | 20,000 |
| share who shop there mainly | 40% | assumption | 8000 |
| trips a week | 1.5 | assumption | 12,000 |
| weeks | 52 | 624,000 | |
| dollars a trip | 60 | assumption | $37M |
Answer: about $37M. Sanity check it before you say anything else: does the per-unit or per-person figure sound like the world you know?
What makes an answer good?
- The chain is named before the numbers. “Population, share who run, pairs a year, price a pair.” Then the arithmetic.
- Each assumption gets one sentence of defense. “Fifteen percent run regularly; that is about one in seven adults, which feels high for the whole population and about right for people under fifty.”
- Rounding is announced. “Call it 60 billion.”
- The result gets a check. A per-person, per-unit or per-day ratio, said out loud.
- The most sensitive assumption is named. The one you would buy data on first.
How do I practice sizing?
Pick one question from the table a day. Build your own chain before reading the one here, time two minutes, then compare the factors, not the answer. If your answer is three times larger, find the one factor that explains most of the gap; it is usually a frequency or a share. With a recorded sizing case in a browser tab, Casepartner shows a math check after each number lands; use it to catch the step where your rounding drifted.
Questions
What are common market sizing questions in consulting interviews?
Counts of things (coffee shops, ATMs, trucks, hotel rooms), spend by a population (pet food, running shoes), and revenue of a single unit (a theater, a supermarket). Ten worked examples are above.
Are the answers on this page correct?
They are what the stated chains give; the arithmetic was run in a script and the page prints it. The assumptions are labeled, and a different defensible assumption gives a different answer, which is how the interview works.
How long should a sizing answer take?
About two minutes: name the chain, defend each assumption in a sentence, multiply with rounding announced, check the result with a ratio, name the most sensitive assumption.
Does Casepartner size the market for me?
No. When a number lands it shows a math check: setup, answer, one sanity ratio. The chain and the assumptions are yours.