TAM/SAM/SOM Estimator
Market sizing goes wrong in two directions: a number so broad it justifies anything, or a number so narrow it describes a fantasy. This estimator turns four planning inputs into three connected figures — total addressable market, serviceable addressable market and serviceable obtainable market — then checks whether the implied share of your serviceable market is plausible. It runs entirely in your browser.
Free tool · nothing is uploaded
Size your market from four numbers
Turn a market count, annual customer value, serviceable share and sales capacity into a connected TAM, SAM and SOM estimate.
- TAM → SAM → SOM
- Serviceable filters
- Capacity check
- Copy-ready summary
Market inputs
Count the companies or accounts that could buy — not every registered business in the economy. Shorthand like 12k or 1.2m works.
Annual contract value, or the yearly value of a typical client. Use one currency throughout; the tool never converts.
Reachable geography × ICP fit. Example: 30% in-region × 50% fit = 15%. Be able to name who you excluded.
New logos you can realistically close after ramp, close rate and delivery capacity. This is the ceiling SOM is built from.
TAMbusinesses × average annual value
SAMTAM × serviceable share
SOMthe lower of SAM and capacity × annual value
Estimate
Your estimate will appear here
Enter a market count, annual value, serviceable share and 12-month capacity to build the funnel.
SOM · obtainable in 12 months
—
SOM appears when all four inputs are valid.
Incomplete Add your market inputs to begin.
$ is a display label only. Every amount is read in the same currency; no conversion is applied.
Assumption check
- TAM — Total addressable market
- SAM — Serviceable share × TAM
- SOM share — of SAM
- Capacity ceiling — Capacity × annual value
This model reads SOM/SAM as Conservative below 2%, Credible from 2% to 10%, Stretch above 10% to 25%, and Ambitious above 25%. When capacity reaches or exceeds SAM, SOM is capped at SAM.
- Info Enter your market inputs to see the assumption check.
Planning estimate: one currency, a 12-month horizon, no growth, churn or price changes. It is not a forecast.
What TAM, SAM and SOM mean
The three numbers describe progressively smaller markets. TAM is the whole opportunity if every possible customer bought. SAM is the part your offer, geography and model can actually serve. SOM is the part you can realistically win in a defined period — here, 12 months.
| Metric | Question it answers | Formula used here |
|---|---|---|
| TAM — total addressable market | What is the annual value of every customer who could conceivably buy this category? | Target businesses × average annual value per customer |
| SAM — serviceable addressable market | What slice can we actually reach and serve with this offer? | TAM × serviceable share |
| SOM — serviceable obtainable market | What can we realistically win in the next 12 months? | The lower of SAM and 12-month customer capacity × annual value |
A TAM without a SAM is a headline. A SAM without a SOM is a plan that nobody has costed against sales capacity. The estimator keeps all three connected so that a change in any input moves the whole funnel.
How this estimator works
The model is deliberately bottom-up on both ends. TAM is built from a customer count and an annual value, not copied from a report. SOM is built from the number of customers you can win, not from a market-share percentage someone liked in a pitch deck.
- TAM multiplies the number of target businesses by the average annual value of one customer.
- SAM applies one serviceable share to TAM. That share should combine reachable geography and ICP fit, and every filter should have a reason.
- Capacity ceiling multiplies the number of new customers you can win in 12 months by the same annual value.
- SOM takes whichever is smaller: the capacity ceiling or SAM. You cannot win more customers than the serviceable market contains.
- Implied share divides SOM by SAM. The tool uses that share to label the plan Conservative, Credible, Stretch, Ambitious, Capped, or one of the zero-market states.
This is a planning model, not a forecast. It does not compound growth, subtract churn, change prices, model seasonality, or simulate a funnel. Those choices are intentional: a small number of honest inputs is more useful than a spreadsheet that looks precise because it has twenty assumptions.
How to choose the four inputs
Total businesses in your market
Start from a definition you can defend in one sentence: for example, “independent marketing agencies with 5–50 employees in the United States.” Then count that group, or estimate it from a credible directory or industry list. Avoid counting every registered company in a country unless every one of them could genuinely buy.
If you use a shorthand suffix, 12k means 12,000 and 1.2m means 1,200,000. The field accepts commas and spaces. A whole number is required because a fraction of a business is not a customer.
Average annual value per customer
Use the amount one customer pays you in a year, not their revenue. If you sell a one-off project, annualize the value of a typical client relationship over 12 months. If you have several tiers, use a weighted average or run the estimate once per tier.
This one input drives all three market values, so it deserves the most care. A vague “somewhere between $5,000 and $50,000” produces a vague market. Pick a number, write down why, and test the sensitivity by changing it later.
Share of that market you can actually serve
This is the most abused input in market sizing. A serviceable share is not a wish; it is a filter. Multiply the reachable geography by the share that fits your ICP. If you can serve 30% of the market by location and 50% by segment, the combined share is 15% (0.30 × 0.50), not 80%.
For a tightly focused B2B offer, a single-digit serviceable share is a reasonable starting point. A high share is not automatically wrong, but it should survive the question: “Who exactly is excluded, and why?”
New customers you can win in 12 months
This is a capacity assumption, not a hope. Work backwards from the sales motion: conversations started per month, the share that become qualified, the close rate, the length of the cycle, and the delivery capacity behind it. A solo consultant and a five-person sales team should not enter the same number.
If you expect a ramp, count only the customers you can realistically close in the period, not the run-rate you might reach at the end of it. The tool then shows whether that capacity implies a credible share of SAM.
Worked example
The built-in B2B SaaS example uses a market of 12,000 target businesses, an average annual value of $18,000, a 15% serviceable share, and capacity for 60 new customers in 12 months.
| Step | Calculation | Result |
|---|---|---|
| TAM | 12,000 × $18,000 | $216,000,000 |
| SAM | $216,000,000 × 15% | $32,400,000 |
| Capacity ceiling | 60 × $18,000 | $1,080,000 |
| SOM | Lower of $32,400,000 and $1,080,000 | $1,080,000 |
| Implied share of SAM | $1,080,000 ÷ $32,400,000 | 3.3% — Credible |
These are outputs from the model, and the inputs are illustrative. They are not benchmarks or research findings. What matters is the reasoning: the capacity ceiling is well below SAM, so the plan is capacity-limited and the implied share is modest. If capacity were 2,000 customers instead, the ceiling would exceed SAM and the tool would cap SOM at SAM.
How to read the status label
The status is a second opinion on the relationship between SOM and SAM, not a grade of your business. The thresholds below are planning bands built into this tool, not industry benchmarks.
| Status | When it appears | What to check |
|---|---|---|
| Conservative | SOM is below 2% of SAM | Is the capacity assumption too low, or is the market genuinely small? |
| Credible | SOM is 2% to 10% of SAM | Can the sales motion actually produce that many customers? |
| Stretch | SOM is above 10% and up to 25% of SAM | What would have to be true about differentiation, demand and delivery? |
| Ambitious | SOM is above 25% of SAM | Is the market defined too narrowly, or the capacity assumed too high? |
| Capped at SAM | Capacity would cover the whole serviceable market | Widen the filters or lower the capacity assumption; SOM cannot exceed SAM. |
| No market / No capacity | Serviceable share or capacity is zero | The model cannot produce a positive SOM from a zero input. |
If the status surprises you, change one assumption at a time. A market sizing model is most useful when it shows which assumption is doing the work.
Capacity-based SOM versus a market-share assumption
Many templates calculate SOM as “SAM × expected market share.” That is arithmetically simple but analytically weak: the share is usually a guess, and a guess can be adjusted until the answer looks appealing. This estimator reverses the logic. It turns sales capacity into revenue, then shows the share of SAM that revenue implies.
Both views are useful. If you already have a target share, divide it into SAM to see how many customers and how much sales capacity it requires. If you have a capacity plan, use this tool to see whether the share is plausible. The point is to make the assumption visible rather than hide it inside a percentage.
Limitations
- Inputs are assumptions. The tool cannot verify your market count, annual value, serviceable share or capacity. Its output is only as good as those four numbers.
- It is a 12-month snapshot. There is no growth, churn, expansion revenue, price change or seasonality. Running the same inputs for a different horizon requires a different capacity estimate.
- SAM filters are manual. The tool does not know which geographies you can serve or which accounts fit your ICP. It applies the share you give it.
- No currency conversion. Every value is read in one currency. Mixing currencies will produce a meaningless total.
- No funnel simulation. Close rates, reply rates and delivery capacity are meant to be baked into the customer-capacity input, not modelled separately.
- Not a forecast or a valuation. A market estimate is one input to planning. It is not evidence of demand, and it does not replace conversations with real buyers.
- Rounding is for display. The large result and funnel use compact notation (for example, $1.08M). Exact figures appear in the TAM tile, the SOM line and the copied summary. Calculations use the unrounded numbers.
Frequently asked questions
Is SOM a prediction of next year’s revenue?
No. It is a capacity-based ceiling: the revenue you would produce if you won every customer your 12-month capacity allows, capped by the serviceable market. Real revenue will usually be lower because demand, timing and execution are not guaranteed.
Should I enter customer revenue or my price?
Enter what one customer pays you per year. If you sell a subscription, that is the annual contract value. If you sell a project, annualize the value of a typical client relationship over the same 12-month horizon.
Why is SOM capped at SAM?
Because SOM is a subset of SAM. If your capacity suggests you could win more customers than the serviceable market contains, the estimate is market-limited rather than capacity-limited. The honest conclusion is that the capacity number, the serviceable filters, or the timeframe needs revisiting — not that you can own more than 100% of SAM.
Does the tool work for B2C or local businesses?
Yes, if you map the idea sensibly: households or individuals become the “businesses” count, and the annual value is what one household or client spends with you. The capacity input usually needs a different unit, such as clients served per month rather than logos closed by a sales team.
What counts as a reasonable serviceable share?
There is no universal number. A focused B2B offer with a specific geography and company size might reasonably use a single-digit share. A broad consumer product in one country can be much higher. What matters is that each filter is explicit and defensible, not that the percentage matches a benchmark.
Why does the same number show as a compact value and an exact value?
The primary result and funnel use compact notation so the shape of the market stays readable. Exact figures appear in the TAM tile, the SOM line and the copied summary. No calculation is rounded; only the display is shortened.
Can I save or share an estimate?
The tool does not store anything. Use Copy estimate to copy a plain-text summary into a document, email or spreadsheet. Nothing is sent to a server, and no cookie or local storage is used.
Related tools
- ICP Builder — define the segment that becomes your serviceable share.
- Lead List Quality Scorer — check whether your list matches the market you sized.
- Account Tiering Tool — split the target market into A, B and C accounts.
- Lead Scoring Calculator — turn fit and intent into a prioritisation score.
Next step
A market estimate is more useful when it becomes a list you can work. If you are turning a TAM/SAM/SOM model into a prospecting plan, see how mizanursguide.com builds B2B lead generation systems that connect targeting, list quality and outreach.