A market-sizing question asks you to estimate spend or volume in a defined market with a transparent chain. Interviewers are not grading whether you know Kenya’s GDP. They are grading whether you pick the right object, keep units, and sanity-check.
This page owns question types and how to start. A full size with an assumptions table lives on step-by-step market sizing. Pure “how many” counts with no price live on guesstimates.
What a sizing question sounds like
| Flavor | Example | Output |
|---|---|---|
| Value ($ / year) | “US spend on warehouse HVAC service contracts” | $ / year |
| Volume (units / year) | “Bags of bagged cement sold in Kenya each year” | tonnes or bags / year |
| Installed base | “How many commercial aircraft in the US fleet” | stock, not flow |
| Constrained supply | “MRI scans a county hospital can run” | capacity, then demand if asked |
If they say “market,” default to $ / year unless they name units. If they say “how many,” default to count, and ask whether they want a stock or a flow.
Clarify in one breath: geography, product, customer, year, and value versus volume.
How they grade you
- Object. Bagged retail cement is not ready-mix and not clinker exports.
- Chain. Three to six factors you can defend. Not a data dump.
- Units. People × kg/person/year = kg/year. Then bags.
- Sanity. Compare to a known ceiling (capacity, imports, a comparable country).
A beautiful number with the wrong object is a zero.
Sketch: bagged cement in Kenya (volume, not a full TAM)
This is a start, not the full worked size (that format is the other article). Use it to see a volume chain.
Question. How many 50 kg bags of cement are sold in Kenya per year for small construction (not bulk to big contractors)?
Object. Bagged, domestic retail + small builder. Exclude bulk tanker to mega-projects if the interviewer agrees.
Demand chain (household + small builder):
- Population ~55 million.
- Households: 55m / 4.5 ≈ 12 million households.
- Share doing a cement job this year (floor, rooms, small shop): 8% → 0.96m households.
- Cement per job: a small room/floor job ~1.5 tonnes (30 bags). Many jobs are smaller; blend 1.0 tonne = 20 bags.
- 0.96m × 1.0 t = 0.96 Mt.
- Plus small commercial (kiosks, walls): add ~40% → ~1.3 Mt bagged.
Bags. 1.3e6 t / 0.050 t per bag = 26 million bags / year.
Sanity (supply). Kenya cement nameplate is on the order of several Mt; a large share is bulk and infrastructure. 1.3 Mt bagged for the small-builder channel is a slice, not the whole industry. If your number were 20 Mt bagged, you just sized the entire economy’s cement as retail bags — too high.
Present as order of 25 million 50 kg bags, plus/minus a factor of two, driven by “jobs per household” and “tonnes per job.”
Do not stop at 26,000,000 as if it were a census.
Types that trick people
Stock vs flow. “How many MRI machines in France?” is a stock. “How many scans?” is a flow. Mixing them produces machines × scans without a utilization.
B2B vs consumer. Cement in Kenya can be demand-side (households) or supply-side (kiln output × bag share). Pick one; use the other as the check.
Value with no price. If they want $, you need $/bag. If you do not know price, bound it (a 50 kg bag at a Nairobi hardware shop is a few hundred KES — ask or state a placeholder) and keep going. The step-by-step article is where a full $ TAM with a price table belongs.
When a “sizing question” is not a sizing question
They already gave you volume on an exhibit. Read the exhibit. Do not resize the US.
They asked whether to enter. Size is one input to market entry, not the whole case.
They asked why profit fell. Sizing the industry will not isolate the driver.
The mistake unique to sizing questions (as a type)
Treating every sizing prompt as US households × $100. Kenya bagged cement does not start at 330 million Americans. The unique fail on this page’s territory is template panic: candidates hear “size the market” and paste a US consumer funnel onto a B2B or emerging-market volume question. Change the first factor to match the object.
Second unique fail: answering $ when they asked bags, or bags when they asked $.
What to say first
“I will size bagged 50 kg cement in Kenya for small builders, in bags per year, demand-side, then check against national cement output. I need to exclude bulk infrastructure unless you want the whole industry.”
Then write the chain. Then one sanity bound.
Practice the chain, not a memorized TAM
Timed market-sizing drills randomize the object so you cannot paste last week’s funnel.