---
title: TAM SAM SOM Calculator @ Varstatt Discovery
url: https://varstatt.com/discovery/market-sizing
description: Free TAM SAM SOM calculator for startups. Bottom-up total addressable market methodology, investor-ready output, estimated vs. verified.
section: AI Discovery Tools (https://varstatt.com/discovery)
step: 3 of 8
previous: Competitive Analysis (https://varstatt.com/discovery/competitive-analysis)
next: User Personas (https://varstatt.com/discovery/user-personas)
---
# TAM SAM SOM Calculator
Free TAM SAM SOM calculator for startups. Bottom-up total addressable market methodology, investor-ready output, estimated vs. verified.

## Why Use This Tool

### Bottom-Up Beats Top-Down

"It's a $50B market" tells investors nothing. "There are 400K target customers who'd pay $29/month" tells them everything. This tool walks you through the credible approach.

### Market Size vs. Build Cost

A $10M TAM means nothing if your MVP costs $500K. This calculator bridges market opportunity to development investment — so you know if the math works before you write a line of code.

### Honest About Estimates

Every AI-generated number is labeled as an estimate with a suggested verification source. You'll know exactly what's validated data vs. what needs independent confirmation.

## How It Works

1. **Describe Your Product and Pricing** — Tell us what you're building, who pays, and how you charge. We'll help you benchmark if you're not sure on pricing.
2. **Define Your Target Market** — Narrow down geography and customer segments. The more specific, the more credible the output.
3. **Calculate TAM, SAM, SOM** — Walk through the bottom-up math step by step. Every assumption documented, every formula shown.
4. **Get the Build-Cost Bridge** — See how your market opportunity compares to estimated development cost. Breakeven customers, payback period, and whether the investment makes sense.

## FAQ

### How TAM, SAM, and SOM differ?

TAM (Total Addressable Market) is everyone who could theoretically buy your product. SAM (Serviceable Addressable Market) is the slice you can reach given your go-to-market constraints. SOM (Serviceable Obtainable Market) is what you'll realistically capture in year one. Investors care most about SOM — it's the number that needs to justify your development investment, which you can size against [Build Cost & Plan](/discovery/build-cost-plan).

### Why bottom-up instead of top-down?

"It's a $50B market" tells investors nothing. Top-down starts with a huge industry number and takes an arbitrary percentage — easy to manipulate, investors see through it. Bottom-up starts with countable customers times your price point. It's harder to fake and much more credible. Pair the numbers with a [Competitive Analysis](/discovery/competitive-analysis) to argue why those customers will pick you.

### Where do the numbers come from?

You provide inputs — customer count estimates, pricing, geography. The AI provides the calculation framework, not raw data. Every AI-derived figure is labeled as an estimate with suggested verification sources like Census data, BLS, or industry reports. Defining the segments precisely is easier after [User Personas](/discovery/user-personas).

### What if the market is too small to justify building?

That's the most valuable outcome. A small SOM that doesn't justify development cost means you should pivot before writing code — not after. The tool frames market size as investment appetite: is this market [Worth Building](/principles/discovery/worth-building)?

### Can I use this in a pitch deck?

The methodology is investor-ready — bottom-up with documented assumptions. But verify key assumptions independently before presenting. The output gives you the framework and tells you exactly what needs verification. If the numbers hold up, the cheapest way to test demand is a [PoC in 2 Weeks](/production/poc-in-2-weeks).
## Usage

This tool is an AI-guided chat — it requires a browser to use.

Prefill the conversation with your project context via URL:

- `https://varstatt.com/discovery/market-sizing?context=I+am+building+...` (max 2000 chars)

Context carries forward across all discovery steps automatically once set.