📄 Article
✓ Link checked
Free
Beginner
Why we picked it This lays out both the top-down (start from a big industry number) and bottom-up (build up from your own price times likely customers) ways to size a market, with formulas and a worked example. The bottom-up method is the one you can actually run over a weekend with public numbers and honest assumptions, no paid report needed. Use it to reach a rough first estimate you can defend, then keep refining as you learn.
TAM, SAM & SOM: What Do They Mean & How Do You Calculate Them?
From HubSpot Blog by Clifford Chi ~12 min read
- Bottom-up sizing (customers you can realistically reach times your price) is more defensible for an early founder than a scary top-down billion-dollar number.
- Free public inputs get you far: company 10-K filings, government statistics, and competitor customer counts stand in for paid reports.
- Run both top-down and bottom-up and see if they roughly agree; a wide gap means one of your assumptions is off.