How to build a structured market-sizing estimate

"How many cricket bats are sold in India every year?" Nobody expects you to know. Market-sizing questions test whether you can reach a reasonable answer through clear logic — and whether you can explain that logic so someone else can check it.

Step 1: Define exactly what you are sizing

Most weak estimates go wrong before any maths happens, because the question was never pinned down. Settle these first:

• What — new bats only, or second-hand too? Leather-ball bats, tennis-ball bats, or both?
• Who — consumers only, or schools and clubs as well?
• Where and when — all of India, for one year.
• Volume or value — number of bats, or rupees spent?

State your choices out loud. "I'll size the number of new bats bought by individuals in India in a year, and add institutional buyers at the end if we have time."

Step 2: Choose a route

There are two broad approaches.

Top-down (demand side) starts from a population and narrows it: people → relevant segment → share who buy → how often they buy.

Bottom-up (supply side) starts from the sellers: number of outlets or manufacturers → how much each sells or makes.

When you have time, do one and check it with the other. If they land in a similar range, you can be more confident. If they do not, the gap tells you which assumption to revisit.

Step 3: Build the chain, with every assumption visible

Here is a top-down estimate. The figures below are illustrative assumptions for practice, not data. In an interview, you would state each one and give a one-line reason.

The last step divides 5.6 crore by 3, which gives about 1.87 crore — call it roughly 1.9 crore bats a year.

Step 4: Find the assumption that matters most

Look at which input the answer is most sensitive to. Here, bat ownership is the shakiest assumption. If only 5% own a bat, the answer halves to under 1 crore; at 15% it rises to about 2.8 crore. Saying this out loud — "ownership is my least certain assumption, and the answer scales directly with it" — shows the interviewer you understand your own estimate.

Try it yourself in the market-sizing builder: change one assumption at a time and watch how far the answer moves.

Step 5: Sense-check from another angle

A quick supply-side check: suppose there are a few lakh shops across India that sell sports goods, and a typical one sells a bat or two a week. A couple of lakh shops selling around 80 bats a year each gives roughly 1.6 crore bats — in the same range as our top-down figure. Again, these are assumptions; the point is that two independent routes roughly agree.

Getting comfortable with Indian number units

Estimates in Indian business conversations often switch between lakh, crore, million and billion. Keep these conversions to hand:

• 1 lakh = 100,000
• 10 lakh = 1 million
• 1 crore = 10 million
• 100 crore = 1 billion

Pick one system for the whole estimate and convert only at the end. Most arithmetic slips in market sizing come from mixing units halfway through.

Common mistakes

• Starting the maths before defining the market.
• False precision. "1,86,66,667 bats" is not more accurate than "about 1.9 crore". Round as you go.
• Hidden assumptions. If an assumption is not said out loud, the interviewer cannot give you credit for it — or help you fix it.
• No sense check. An answer that implies every Indian buys three bats a year should stop you in your tracks.

For more practice, the case prompts include market-sizing questions alongside other case types.