Treat market sizing as a transparent estimate, not a forecast. Define the product, buyer, geography and time horizon first. Then estimate the relevant customer or purchasing units from evidence and realistic price assumptions; cross-check against competitors and external sources. SBA guidance recommends specifying the target market and examining competitors by product and market segment.
Direct answer
Treat market sizing as a transparent estimate, not a forecast. Define the product, buyer, geography and time horizon first. Then estimate the relevant customer or purchasing units from evidence and realistic price assumptions; cross-check against competitors and external sources. SBA guidance recommends specifying the target market and examining competitors by product and market segment.
A practical sequence
- Name who buys, what they buy and where.
- Build an assumption-led bottom-up range from identifiable buyers and purchase frequency.
- Separate the total category from the initial segment you can serve and reach.
- Cross-check against independent market data and competitor segments.
- State the source date, formula, uncertainty and assumptions.
Limits and boundaries
Market size does not demonstrate urgency, access to distribution, willingness to pay or profitable unit economics. Avoid false precision, double counting and using broad industry revenue as a startup forecast.
Sources and review
- U.S. Small Business Administration — Plan your businessAuthoritative context for this original educational answer.
General education, not individualized business, investment, legal, technical or regulatory advice. Reviewed 31 October 2026. Context and requirements vary; consult qualified specialists where appropriate.