Enter your potential customers and annual revenue per customer to size the market.
What TAM, SAM, and SOM actually mean
The three numbers answer three different questions, from widest to narrowest. TAM (total addressable market) is the whole pie: everyone who could conceivably buy this kind of product, times what each would pay per year. SAM (serviceable addressable market) is the slice your specific product can actually serve, once you account for the segment, geography, and budget you realistically target. SOM (serviceable obtainable market) is the bite you can realistically take, given competition and your own reach, usually over the next few years.
A common mistake is stopping at TAM because it is the biggest and most impressive number. TAM tells you whether a market is large enough to bother with. SOM tells you whether the business is worth building right now. Investors and honest founders care most about SOM, because it is the number tied to what you can actually earn.
How to calculate TAM, SAM, and SOM
The calculator uses the top-down method, which is the fastest way to a first estimate:
- TAM = total potential customers x annual revenue per customer
- SAM = TAM x the percentage of the market your product can serve
- SOM = SAM x the percentage of that serviceable market you can realistically win
Top-down vs bottom-up sizing
Top-down starts from a big market figure and narrows with percentages. It is quick, but the percentages are guesses, so it is easy to fool yourself with an optimistic SAM or SOM. Use it for a first pass.
Bottom-up starts from your own unit economics: how many customers you can actually reach through each channel, times your real price. It takes more work but is far harder to fake, because every number ties to something you can defend. The strongest market sizing does both and checks that they roughly agree. If your top-down SOM is 50 times your bottom-up estimate, one of them is wrong.
Where the market really is: real demand, not just math
A market-size model is only as good as the assumption that people actually want the thing. The number can look enormous and still describe a market that does not feel the problem enough to pay. That is why sizing should come after you have confirmed the pain is real, not before.
The honest sequence is: find a specific, recurring problem people already complain about, confirm they are spending time or money on a workaround, and only then size the market for solving it. You can browse real, scored customer pain points on the explore page to ground your sizing in demand that actually exists, rather than a market that only exists in a spreadsheet.
Frequently asked questions
What is the formula for TAM, SAM, and SOM?
TAM equals total potential customers multiplied by annual revenue per customer. SAM equals TAM multiplied by the share of the market your product can serve. SOM equals SAM multiplied by the share of that serviceable market you can realistically capture.
What is a good SOM percentage?
There is no single right number, but a realistic early SOM is usually a small single-digit percentage of SAM, because you are competing for a slice of an already-narrowed market. A SOM that is a large fraction of SAM is a red flag that the estimate is too optimistic.
What is the difference between TAM, SAM, and SOM?
TAM is the entire market for this type of product. SAM is the portion your specific product can serve given your segment and reach. SOM is the portion of SAM you can realistically win in the next few years. They go from widest and most theoretical to narrowest and most actionable.
Should I use top-down or bottom-up market sizing?
Use both. Top-down (starting from a big market figure and applying percentages) is fast but easy to inflate. Bottom-up (starting from customers you can actually reach times your real price) is harder to fake. When they roughly agree, you can trust the estimate.
Is this TAM SAM SOM calculator free?
Yes. It runs entirely in your browser, there is no signup, and nothing you type is sent anywhere. IdeaFast makes money from its research product, not from tools like this one.
Do I need to size the market before validating my idea?
No, and doing it first is a common trap. Confirm the problem is real and that people pay to work around it, then size the market for solving it. A huge TAM for a problem nobody feels strongly about is not a business.
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