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TAM SAM SOM Calculator: Market Size Model with TAM Sanity Check

Size your market the way investors trust. Build a bottom-up model (customers × annual price) or a top-down one, narrow it to SAM and SOM, and check whether the TAM claimed in a deck is realistic or inflated.

QUICK ANSWERTAM (total addressable market) = all potential customers × annual revenue per customer. SAM = the part you can serve with your product, channels and geography today. SOM = the share of SAM you can realistically win in 3–5 years, usually 1–5%. Investors trust bottom-up TAM far more than top-down industry reports.

TAM = Customers × Annual price (bottom-up)
SAM = TAM × Serviceable %
SOM = SAM × Achievable share %

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What the TAM SAM SOM Calculator & TAM Sanity Checker does

✅ Bottom-up and top-down methods
✅ TAM, SAM and SOM
✅ Customers needed for SOM
✅ Claimed TAM sanity check
✅ Year-5 plan vs SOM check

How to use the TAM SAM SOM Calculator & TAM Sanity Checker

STEP 1
Enter your numbers
Type the figures you know. Every field starts with a realistic example so you can see how it works.
STEP 2
Read the result instantly
Results, tables and the plain-English explanation update as you type. No submit button, no login.
STEP 3
Test scenarios
Change one assumption at a time (valuation, growth, dilution, exit) to see what really moves the outcome.
STEP 4
Share or save
Copy the summary, send it on WhatsApp or print to PDF for your co-founders, board or investment committee.

Why bottom-up market sizing wins

“India’s ₹50 lakh crore retail market” tells an investor nothing about your business. “6 lakh private schools × ₹40,000 a year” shows you know your customer, your price and the realistic ceiling.

A credible SOM, tied to your sales capacity and channels, also anchors your revenue plan. If year-5 revenue exceeds SOM, one of the two is wrong.

Worked example

60 lakh target small businesses × ₹12,000 a year = ₹7,200 Cr TAM. With 25% serviceable today, SAM is ₹1,800 Cr; a 3% share gives a SOM of ₹54 Cr, or 45,000 paying customers.

Frequently asked questions

What is the difference between TAM, SAM and SOM?

TAM is the whole market for your product type, SAM is the part you can serve today, and SOM is the part you can realistically win in the next few years.

How big does a TAM need to be for VC?

Large enough that a realistic share supports a company worth thousands of crores. Many Indian VCs want to see a path to ₹1,000 Cr+ revenue potential.

How do I sanity-check a claimed TAM?

Rebuild it bottom-up and compare. If the claimed TAM is several times your bottom-up number, it is probably top-down or includes segments the product cannot serve.

Is this tool free? Do I need to sign up?

Yes. It is completely free, needs no login and has no usage limit. FastFee builds payment collection software; these startup and investor tools are free resources for founders, angels and fund managers.

Is my data private?

Yes. Everything you type stays in your own browser on this device (local storage). Nothing is uploaded to FastFee. Export or print a copy if you need to keep it.

Use it together with

Competitor Mapping & Market Map Tool →Competitor feature grid plus a 2×2 positioning map you can print for your deck.Category Saturation Analyzer →Score sector crowding from funded competitors, late-stage leaders and capital vs market size.Startup Red Flag Detector & Claim Verifier →Flags unusual growth, margins, runway, concentration and cap table issues, with how to verify each claim.

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