Input accuracy
Are you using real, current numbers — not rough guesses that flatter the result?
Skip or Ship — Free Calculators
Market Size Calculator (TAM/SAM/SOM)
Calculate Total Addressable Market, Serviceable Addressable Market, and Serviceable Obtainable Market for your pitch deck or business plan. Free, no signup.
Benchmark fit
Is your result healthy for your specific business model, not just positive?
Sensitivity
Which single input, if wrong, would change the result most?
Time horizon
Does this hold up over 12 months, or only at today's volume?
Next decision
What should change in the business because of this number?
TAM/SAM/SOM sizing gets a bad name because most founders inflate it — 'the global market is $500B, if we capture just 1%...' is the fastest way to lose investor trust.
This calculator forces bottom-up sizing: start from a real buyer count and real spend per buyer, then narrow down honestly. That's the version investors actually believe.
Free calculator
Market size calculator (TAM / SAM / SOM)
Bottom-up market sizing: total buyers × annual spend, narrowed down to what you can reach and realistically win.
£/yr
%
%
Results
TAM (total market)£60.00M
SAM (serviceable)£12.00M
SOM (obtainable)£1.20M
A good number doesn't mean a good idea.
Get the full Ship, Fix, or Skip verdict — free, 30 seconds, no signup.
TAM, SAM and SOM defined
TAM (Total Addressable Market) is the revenue opportunity if you captured 100% of the market — an upper bound, not a target. SAM (Serviceable Addressable Market) is the slice you can actually reach given your geography, language, and business model. SOM (Serviceable Obtainable Market) is what you could realistically win in the next 2–3 years given competition and your resources.
Bottom-up beats top-down every time
Top-down sizing starts with a huge global number and applies an arbitrary percentage. Bottom-up sizing starts with a specific buyer count (e.g. '4,200 UK accounting practices with 5–20 staff') and a realistic spend per buyer, then works up. Investors can sanity-check bottom-up numbers; they instantly discount top-down ones.
How this calculator works
- Enter the total number of potential buyers in your specific category.
- Enter what one buyer would realistically spend per year on this solution.
- Enter the percentage of that market you can actually reach (SAM).
- Enter the percentage of the reachable market you could realistically win in ~3 years (SOM).
Direct answer — Market Size Calculator (TAM/SAM/SOM)
Calculate Total Addressable Market, Serviceable Addressable Market, and Serviceable Obtainable Market for your pitch deck or business plan. Free, no signup.
Stop reading. Get your verdict.
Describe your idea and the Skip or Ship engine returns a Ship, Fix, or Skip verdict with a full 10-category score breakdown — free, in 30 seconds, no signup.
Frequently asked questions
How do I calculate market size (TAM, SAM and SOM) for a startup?
Bottom-up, not top-down: count your specific potential buyers (TAM), multiply by realistic annual spend per buyer, then narrow to the share you can actually reach given geography and channel (SAM), and the share you could realistically win in 2–3 years given competition (SOM). Enter those four numbers above and the calculator does the rest.
What's a good SOM percentage for a pitch deck?
Most credible SOM estimates land between 1% and 10% of SAM within 3–5 years, depending on competition density and your distribution advantage. Anything above 20% needs an unusually strong justification.
Do investors actually care about TAM?
They care about TAM as a ceiling check — is the market even big enough to build a venture-scale business — but they weight SAM and SOM far more heavily when assessing near-term viability.
Can a small TAM still be a good business?
Yes. Many highly profitable indie businesses operate in TAMs under £50M because they own the niche completely and charge premium prices. Small TAM only matters if you need venture-scale returns.
Related pages
Last reviewed
Ready to pressure-test this idea with live market signals?
Validate your idea now