TAM, SAM, SOM
Three nested estimates of market size: total demand, the slice you can serve, and the share you can realistically win.
TAM, SAM, and SOM are three layers of market sizing. TAM (Total Addressable Market) is everyone who could ever want the product. SAM (Serviceable Addressable Market) narrows that to the segment your offering and reach actually fit. SOM (Serviceable Obtainable Market) is the realistic share you can capture in the near term given your resources.
For a founder this framework keeps you honest. A huge TAM looks exciting on a slide, but SOM is the number that tells you whether this can be a real business for you, now, not in theory. It also forces you to define who you're actually selling to.
The hard part is grounding the numbers in real data instead of guesses. How to size your market walks through the method, and Kalit Search pulls market and competitor research from a prompt to back the estimates.