Market Size Calculator (TAM/SAM/SOM)
Sizing your market opportunity.
Calculate TAM SAM SOM market sizing for business planning. Enter tam total to see market size using tam/sam/som methodology with target market share.
What this tool does
This tool calculates market size using TAM/SAM/SOM methodology with target market share.
Enter Values
Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
Market sizing uses three layers: TAM (Total Addressable Market - everyone who could theoretically buy), SAM (Serviceable - within your geographic/product reach), SOM (Obtainable - realistic near-term). This calculator works through all three.
10B TAM × 20% SAM (your region/category) × 5% SOM (realistic 3-year reach) = 100M SOM. Target 2% market share in SOM = 2M target revenue. Fundable for most seed-stage businesses.
Investors want realistic SOM, not impressive TAM. A 100M TAM with credible 5-10% capture story beats 10B TAM with vague 'we'll get 1%'. Ground each layer with specific reasoning.
A worked example
Try the defaults: tam of 10,000,000,000, sam of tam of 20%, som of sam of 5%, target market share of 2%. The tool returns 100,000,000.00. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.
What moves the number most
The result responds to TAM (Total), SAM % of TAM, SOM % of SAM, and Target Market Share. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.
The formula behind this
TAM → SAM → SOM cascade. SAM = TAM × SAM %. SOM = SAM × SOM %. Target revenue = SOM × share %. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.
Using this as a check-in
Re-run this every three months. A single reading tells you where you stand; four readings tell you whether things are improving. The trend matters more than any individual snapshot.
What this doesn't capture
The score is a composite of the inputs you provide. Life context — job security, family obligations, health, housing — doesn't appear in the math but shapes the real picture. Use the number as a prompt, not a verdict.
£10,000,000,000 £ TAM × 20% SAM × 5% SOM × 2% = $100,000,000.00.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
TAM → SAM → SOM cascade. SAM = TAM × SAM %. SOM = SAM × SOM %. Target revenue = SOM × share %.
References
Frequently Asked Questions
Realistic SOM percentages?
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