How to Accurately Estimate User Scale for Product Growth

User scale estimation, derived from market sizing, is a common consulting skill and case‑interview topic used to answer questions like "How many bald people are in China?" or "How much pork will Zhejiang need next year?"

The approach involves defining the problem, breaking it into a calculation formula, and quantifying each metric.

Top‑down method

Also called the supply‑side approach, it is suitable when supply is constrained, such as when driver availability limits ride‑hailing demand on rainy days.

Bottom‑up method

Also called the demand‑side approach, it fits scenarios where supply can meet demand.

These methods are macro‑level, mature, fast, but may lack precision.

When to use user scale estimation

It helps set appropriate growth targets for new product launches, annual planning, and other stages where business goals are unclear.

Why not rely solely on database data

Beyond behavior data, attitude data such as needs, purchase intent, and preferences often cannot be extracted from databases, so surveys are needed; if behavior data is available, predictive models can also be applied.

Estimation process

1. Segment the market into potential, serviceable, obtainable, and exclusive markets.

2. Obtain data through questionnaire sampling to infer overall figures.

3. Acquire overall market data (internal or external) and calculate product metrics like highcase, basecase, and lowcase.

4. Compute detailed demand ratios using segment user‑scale proportion and demand proportion.

Case study

Data collected via questionnaire is shown in the following images: