🌍 Market Size Calculator (TAM, SAM, SOM)
When someone asks 'how big is the market?', a real answer has three layers, not one. TAM is everyone who could ever buy. SAM is the slice you can actually serve (your geography, your niche, your price point). SOM is the share you can realistically win in the first few years. Founders who quote only the giant TAM lose credibility; the honest SOM is what a plan is built on.
The whole universe: every business or person your product could serve, worldwide or in your realistic reach.
Your real geography, niche, and price point as a percentage of everyone. This turns TAM into SAM.
Of the customers you can serve, the realistic slice you capture early. 1 to 5 percent is a credible starting target. This turns SAM into SOM.
TAM (total addressable market)
$1,000,000,000
SAM (serviceable market)
$100,000,000
SOM (what you can realistically win)
$3,000,000
Customers behind your SOM
6,000
The whole market (TAM) is $1,000,000,000 a year, but you do not sell to the whole world. The slice you can actually serve (SAM) is $100,000,000, and the share you can realistically win in three years (SOM) is $3,000,000 from about 6,000 customers. Build your plan on the SOM, quote the TAM only for context, and you will sound like someone who has done the work instead of someone chasing a headline.
Estimates for planning, not financial advice. Your real numbers will vary; that is exactly why you track them.
Does this resonate?
A market big enough is only step one
The size says the opportunity exists. The next questions are what to build and how to reach them first. That is exactly what the idea library and Dee's guidance are for.
Find your spot in the market →Good questions about this math
What is the difference between TAM, SAM, and SOM?
TAM (total addressable market) is everyone who could ever buy, the whole pie. SAM (serviceable addressable market) is the slice you can actually reach given your geography, niche, and price. SOM (serviceable obtainable market) is the portion of that slice you can realistically win in the near term against real competition. They go from dream to plan, largest to smallest.
Why not just pitch the huge TAM?
Because experienced investors and lenders have heard 'it's a billion dollar market' a thousand times, and it signals you have not thought hard. The number that earns trust is the SOM: a credible, near-term target you can defend with a go-to-market plan. Lead with TAM for scale, but let SOM carry the argument.
What is a realistic share to win?
For a new business against established players, 1 to 5 percent of your serviceable market in the first few years is a credible, ambitious-but-honest range. Claiming 20 or 30 percent out of the gate reads as naive unless you have a genuine structural advantage. Start conservative; beating your own number is a good problem.
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