The Market Sizing Calculator

Help me size this market credibly (TAM / SAM / SOM).

The product and who buys it: [DESCRIBE]
What I know about the market: [DESCRIBE]

Provide:
1. Total addressable market, built bottom-up (number of potential buyers ×
   realistic spend), not top-down
2. The serviceable portion I can actually reach and serve
3. A realistic share I could capture in a few years, with the logic
4. The assumptions behind each number and how to sanity-check them
5. Why the bottom-up number matters more than a big top-down figure

Show the calculation. Flag every input as [VERIFY WITH RESEARCH] — market
sizes are where founders fool themselves and investors.