Free template · GTM strategy & ICP
TAM / SAM / SOM Calculator
Size your market bottom-up by segment: companies, ICP fit, contract value and realistic share.
What's inside
- Up to 15 segments, sized bottom-up
- Automatic TAM, SAM and SOM per segment and in total
- Clear definitions of each level
- An example row to show the format
Who it's for
Founders preparing a fundraise or choosing which segment to attack first.
Why it matters
Most early market sizing starts from a top-down industry report and a hopeful percentage. Investors see through it, and it tells you nothing about who to sell to first. Counting real companies per segment, then filtering for ICP fit, gives you a number you can defend and a list of segments you can actually reach.
Bottom-up sizing also forces useful choices. When you put contract value and a realistic three-year win share next to each segment, you can compare a large segment you barely fit against a small one you fit well. That comparison is often more valuable than the headline total in a pitch deck.
How to use it
- 1On the Market tab, replace the example row and list each segment you could sell to, such as a stage, region or vertical, up to 15 rows.
- 2Enter the number of companies in each segment, using a data provider count or a filtered LinkedIn company search, and note the source somewhere you can find it again.
- 3Add the share of those companies that match your ICP and your annual contract value, using real deal sizes where you have them.
- 4Set a conservative share you could win in about three years, then read TAM, SAM and SOM per segment and in the Total row.
- 5Sort your segments by SOM and fit, and use the top one or two to decide where your first outbound and messaging should focus.
Read alongside it
- How to define your ICP (ideal customer profile)
- GTM strategy framework: a step-by-step guide for B2B startups
- How to build a target account list
TAM / SAM / SOM Calculator: FAQ
- How do you calculate TAM, SAM and SOM?
- Bottom-up, TAM is the number of companies in a segment multiplied by your annual contract value. SAM keeps only the share of those companies that fit your ICP. SOM is the share of SAM you can realistically win in a set period, often about three years. Add the segments together for totals.
- What is the difference between top-down and bottom-up market sizing?
- Top-down starts with a large industry figure and takes a percentage of it. Bottom-up counts the actual companies you could sell to and multiplies by what each would pay. Bottom-up is slower to build, but it is easier to defend to investors and it links directly to a target account list.
- What is a realistic SOM percentage for a startup?
- There is no standard figure. Base it on your sales capacity, sales cycle length and current win rate rather than ambition. A useful check is to divide SOM by your contract value and ask whether your team could close that many deals in the period. If not, lower the share.
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