What is TAM SAM SOM?
TAM, SAM and SOM are three nested estimates of market size. TAM (total addressable market) is the total revenue opportunity if every possible customer bought your product. SAM (serviceable addressable market) narrows that to the segment you can actually serve with your current model, geography and pricing. SOM (serviceable obtainable market) is the realistic slice of SAM you can capture in the near term. Read them together: TAM sets the ceiling, SAM proves you know your lane, and SOM is the number you can actually defend.
How this calculator works
One bottom-up formula, no black box:
The formula: TAM = potential customers × average annual contract value SAM = TAM × (SAM % of TAM ÷ 100) SOM = SAM × (SOM % of SAM ÷ 100)
Start with the number of accounts you could realistically sell to, multiply by your average annual contract value, then narrow twice: once for the slice of the market you can actually serve (SAM), and again for the share you can win in the next one to three years (SOM).
Top-down vs bottom-up market sizing
| Approach | How it starts | Investor read |
|---|---|---|
| Top-down | A published analyst market figure, narrowed by percentages. | Fast, but easy to inflate and hard to defend. |
| Bottom-up | Real target accounts times a realistic ACV, summed by segment. | Slower, but credible because every assumption is traceable. |
This calculator uses the bottom-up approach, customers times ACV, because that is the version investors trust.
How to use TAM SAM SOM in a pitch
- Lead with SOM, not TAM. A grounded near-term number does more for credibility than a giant headline figure.
- Show your work. State the customer count, the ACV and each percentage so the math is auditable.
- Tie SAM to your ICP. The serviceable segment should map to the exact accounts your product fits today.
- Make SOM defensible. Base the capture rate on your sales capacity, win rate and competition, not optimism.
Frequently asked questions
What is TAM SAM SOM?
TAM, SAM and SOM are three nested estimates of market size. TAM (total addressable market) is the total revenue opportunity if every possible customer bought your product. SAM (serviceable addressable market) narrows that to the segment you can actually serve with your current model, geography and pricing. SOM (serviceable obtainable market) is the realistic slice of SAM you can capture in the near term given your sales capacity and competition.
How do you calculate TAM, SAM and SOM?
A simple bottom-up version multiplies market size by price. TAM equals total potential customers times average annual contract value. SAM equals TAM times the percentage of that market your product actually fits by segment, geography or use case. SOM equals SAM times the share you can realistically win in the next one to three years. For example, 100,000 potential customers at a $12,000 ACV is a $1.2B TAM, a 30% serviceable segment is a $360M SAM, and a 10% near-term capture is a $36M SOM.
What is the difference between top-down and bottom-up TAM?
Top-down TAM starts with a large published market figure from an analyst report and narrows it with percentages, which is fast but easy to inflate. Bottom-up TAM builds from your own units, the number of real target accounts times a realistic annual contract value, summed across segments. Bottom-up is slower but far more credible with investors because every assumption is traceable to something you can defend. This calculator uses the bottom-up approach, customers times ACV.
Why do investors care about TAM SAM SOM?
Investors use TAM, SAM and SOM to judge whether a company can grow large enough to return their fund. TAM signals the ceiling of the opportunity, SAM shows you understand who you can actually serve, and SOM shows a grounded near-term revenue plan. A credible, well-sourced SOM often matters more than a huge TAM, because it proves you can convert market size into real revenue rather than quoting an inflated headline number.