Market Sizing Calculator (TAM SAM SOM)
Estimate your Total, Serviceable, and Obtainable market size from customer and pricing inputs.
Published by Blueprint Dynamics. Planning tools, not professional advice. Read the formula, assumptions, and examples below before relying on a result. Independent professional review is not claimed. Learn more about our methodology →
AllTemplates • Blueprint Dynamics • hello@bpdynamics.io. Educational worksheet; entries and assumptions are not independently verified. This document is not tax, legal, medical, investment or engineering approval. Review current official rules and seek a qualified specialist where appropriate.
Scope and reference context
Planning assumptions are not market evidence. Validate customer counts, costs and demand with actual interviews or records; a weighted score does not predict success.
Primary reading context, not an endorsement or evidence that the linked organization reviewed this tool. No independent professional sign-off is claimed.
About the Market Sizing Calculator (TAM SAM SOM)
"How big is the market?" is the question every investor asks and most founders answer badly. The TAM/SAM/SOM framework replaces a hand-waved big number with three nested, defensible figures: the total universe of demand, the slice you could realistically serve, and the portion you can actually capture in the near term. This calculator builds all three from the same handful of inputs so they stay internally consistent.
The value of nesting the estimates is credibility. A giant total addressable market means nothing if you cannot show a serviceable segment you can reach and an obtainable share you can win. By deriving each level from the one above it, the tool prevents the common mistake of quoting an enormous TAM while implying you will somehow capture all of it.
How the Market Sizing Calculator (TAM SAM SOM) works
You enter four numbers: Total Potential Customers, the Serviceable percentage, the Obtainable percentage, and Average Annual Revenue per Customer (ARPC). The tool computes customer counts at each level — TAM customers equal the total, SAM customers equal the total times the serviceable percentage, and SOM customers equal the SAM times the obtainable percentage.
It then multiplies each customer count by ARPC to produce dollar figures. TAM is total customers times ARPC, SAM is serviceable customers times ARPC, and SOM is obtainable customers times ARPC. Because SAM is a fraction of TAM and SOM is a fraction of SAM, the three values are always properly nested, and both the customer counts and the revenue figures update live as you change any input.
Worked example
Start with 1,000,000 Total Potential Customers, a Serviceable share of 20%, an Obtainable share of 5%, and an ARPC of $500. The customer counts come out as 1,000,000 for TAM, 200,000 for SAM (20% of the total), and 10,000 for SOM (5% of the SAM).
Multiplying by the $500 ARPC gives a TAM of $500,000,000, a SAM of $100,000,000, and a SOM of $5,000,000. That $5M SOM is the number that matters for near-term planning — it is the realistic revenue you can pursue now — while the $500M TAM frames the long-run ambition. Presenting all three together shows investors both the ceiling and the credible first target.
Tips & common mistakes
- Build TAM bottom-up from customer counts and ARPC, as this tool does, rather than grabbing a headline industry figure. A derived number is far more defensible in a pitch.
- Keep your Obtainable percentage humble. Capturing more than a few percent of a serviceable market in the early years is rare, so an inflated SOM undermines your credibility.
- Make ARPC realistic and current. Overstating what each customer pays inflates all three figures at once and is the easiest error for a savvy investor to catch.
- Use SOM, not TAM, for your revenue plan. TAM is the opportunity story; SOM is what you can actually book in the foreseeable future.
- Revisit the percentages as you gather real conversion data. Early SAM and SOM are estimates that should tighten as you learn what share you can genuinely win.
Market Sizing Calculator (TAM SAM SOM): frequently asked questions
What do TAM, SAM, and SOM stand for?
TAM is the Total Addressable Market — everyone who could conceivably buy. SAM is the Serviceable Available Market — the portion you can realistically reach given your product, geography, and business model. SOM is the Serviceable Obtainable Market — the share you can actually capture in the near term given competition and resources.
How does the calculator turn customer counts into dollars?
It multiplies the customer count at each level by your Average Annual Revenue per Customer. So TAM dollars equal total customers times ARPC, and SAM and SOM dollars follow from their smaller customer counts. With 10,000 obtainable customers and a $500 ARPC, for example, SOM works out to $5,000,000.
What is a realistic Obtainable percentage to use?
For an early-stage company, a low single-digit share of the serviceable market over the first few years is typical, which is why the default is 5%. Claiming a large obtainable share quickly is a red flag to investors, who know that winning market share against established players is slow and costly.
Why should I build TAM from the bottom up instead of citing an industry report?
A bottom-up figure derived from customer counts and realistic pricing is one you can defend line by line, whereas a top-down industry number is easy to challenge and often includes segments you will never serve. This tool's approach — customers times ARPC — produces the credible kind.
Which figure should I put in my financial plan?
Use SOM. It represents the revenue you can realistically pursue in the near term and should anchor your projections. TAM and SAM tell the story of the long-run opportunity and the room to grow, but planning against TAM would assume a market share almost no company achieves.