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TAM, SAM, and SOM are three views of a market: the full demand for a relevant offer, the part your business can serve, and the part it can realistically win. Calculate each by defining the customer and market first, then applying researched counts, spending, and reach assumptions.
What do TAM, SAM, and SOM mean?
TAM (total addressable market) is the annual value of all demand for the kind of product or service you offer. SAM (serviceable addressable market) narrows that total to customers your business model, geography, and current offer can serve. SOM (serviceable obtainable market) narrows SAM again to the customers you could plausibly reach and win over a defined period.
Keep the customer, need, unit, and time period consistent as you narrow the market. If TAM counts annual spending but SOM counts people, show both measures separately and explain the conversion. SOM is a grounded target, not simply an arbitrary percentage of TAM.
The Market Size Calculator takes a business description, target audience, target market, and language, then produces estimates for TAM, SAM, and SOM. Use the result as a starting point for your own assumptions, not as a substitute for checking them.
How do you calculate TAM, SAM, and SOM?
For a buyer-based estimate, calculate TAM as the total potential customers who fit the need multiplied by annual spend per customer. Calculate SAM using only TAM customers who fit your offer and service area. Calculate SOM using the SAM customers you can reach and convert during the period, multiplied by annual spend per customer.
You can also calculate the revenue view by multiplying the number of eligible customers by their expected annual spend. State whether that spend is a researched current category spend, a price assumption, or an estimate. Do not treat the whole category’s revenue as yours: the market estimate describes potential demand, not your forecast.
How to estimate TAM with a top-down approach
Start with an established population or industry total, then narrow it with evidence-based filters. Define the geography, customer type, and need. Remove groups that do not buy or use this kind of solution, and avoid applying a broad industry total when only a specific subgroup fits.
For U.S. business markets, the Census Bureau’s County Business Patterns provides establishment, employment, and payroll counts by industry and geography. The Bureau of Economic Analysis industry data includes GDP, gross output, and employment measures. These sources can help size business populations or industry context; neither directly tells you how many firms will buy your particular offer. Pick a measure that matches your buyer and explain any filtering assumptions.
How to estimate TAM with a bottom-up approach
Build the estimate from the customers you could identify or count directly. Define the customer unit, such as an organization or an individual, estimate how many meet the need in your target market, and multiply by annual spending for a suitable solution. Use customer interviews, a reliable directory, a survey of a defined group, or official statistics to support the count and spend assumptions.
Bottom-up estimates can be easier to challenge because each input is visible. Check that the customer count does not include the same people twice, that spending is annualized consistently, and that the product can address the need you counted. If one input is uncertain, show a range in your planning rather than presenting a precise total as fact.
How to define SAM and estimate SOM
To get SAM, filter TAM by the customers your current product can serve. Consider the features and delivery model you have, the regions you operate in, the customer sizes you support, and any legal or language constraints relevant to the offer. Recalculate using only customers who meet those conditions.
To estimate SOM, begin with your actual capacity and route to customers. Work out how many eligible buyers your team and channels can reach during the period, then apply a conversion assumption supported by your own sales or test data. If you have no conversion evidence yet, mark SOM as a hypothesis and define a small test that can improve it. Do not claim a market share without stating the buyer count, period, and basis for it.
How to choose market-size inputs
Use sources that measure the same kind of customer and geography as your market definition. Prefer official statistics for broad counts, direct customer research for needs and buying behavior, and your own operating data for reachable volume and conversion. Record the source and date beside each input in your working model, and separate sourced facts from assumptions.
Check that your conclusion changes when uncertain inputs move. A large TAM does not prove demand for your offer, and a narrow SAM may still support a viable business if customers are reachable and the economics work. The market research guide explains how to combine customer, competitor, and market evidence; the one-page business plan guide shows where a market estimate fits in a concise plan.
Use [FounderPal](/) to organize business and audience context into a market-size estimate, then validate the inputs that matter most before using the result to guide your plan.
FAQ
What is the difference between TAM, SAM, and SOM?
TAM is the total annual demand for a relevant market. SAM is the part your current business can serve, and SOM is the part you can plausibly reach and win within a stated period.
How do you calculate TAM?
Define the customer group and need, estimate the number of eligible customers, and multiply by annual spend per customer. Use a top-down population or industry count, or build a bottom-up count from customers you can identify.
Is SOM the same as market share?
SOM can be expressed as a share of SAM, but it should come from a realistic estimate of customers you can reach and convert. State the period and assumptions behind the share instead of choosing a percentage without evidence.
Which is better, top-down or bottom-up market sizing?
Top-down sizing is useful when credible population or industry totals exist, while bottom-up sizing makes customer and spending assumptions visible. Comparing both can reveal where your estimate depends on weak inputs.