How to Calculate TAM SAM SOM for Your Startup

How to Calculate TAM SAM SOM for Your Startup Every investor pitch deck has a market size slide. And most of them are terrible. You've probably seen the pattern: someone Googles a Statista report, slaps a $400 billion number on a slide, and calls it their TAM. The investor nods politely. Then moves on to the next founder who actually did the math. Here's the thing. Market sizing isn't about finding the biggest number you can defend. It's about proving you understand where your customers are, how many of them exist, and what a realistic first year looks like. That's what TAM, SAM, and SOM are for. Let's break down exactly how to calculate each one, with real numbers you can follow along with. What Do TAM, SAM, and SOM Actually Mean? TAM, SAM, and SOM are three layers of market sizing that narrow from the total opportunity down to what you can realistically capture. TAM (Total Addressable Market) is the entire revenue opportunity if you sold to every possible customer. Think of it as the