TAM SAM SOM Calculator

What TAM, SAM and SOM mean

TAM, SAM and SOM are three nested estimates of how big your market is. Investors ask for them because they show two things at once: whether the opportunity is large enough to build a big company, and whether the founders understand which part of it they can actually reach.

• TAM, total addressable market: the total yearly revenue available if every possible customer bought your type of product. It is the ceiling.
• SAM, serviceable addressable (or available) market: the part of TAM your product can serve today, given your geography, language, price point, features and sales channels.
• SOM, serviceable obtainable market: the share of SAM you can realistically win in the next three to five years, given competition and the size of your sales and marketing effort.

A good way to remember it: TAM is the market, SAM is your market, SOM is your revenue target.

How to calculate TAM: two methods

Bottom-up

TAM = Number of potential customers × Revenue per customer per year

You count the customers who could buy, and multiply by what one of them would pay you in a year. This is the method investors trust most, because every number can be checked. The customer count comes from public statistics or industry associations, and the revenue per customer comes from your own pricing.

Top-down

TAM = Total industry revenue from a market report

You start with a published figure for the whole industry and narrow it down with percentages. It is fast, and useful as a cross-check, but the report’s definition of the industry rarely matches your product. A report on “the $500 billion HR software market” says little about a scheduling tool for dental clinics.

Then, for either method:

SAM = TAM × share you can serve  ·  SOM = SAM × share you can win

Worked example: bookkeeping software for small employers

A startup sells bookkeeping software to small US businesses with employees for $50 a month, or $600 a year. According to the SBA Office of Advocacy’s Frequently Asked Questions About Small Business (2026), the US has about 36.2 million small businesses, and 17.7% of them have employees. That is roughly 6.4 million employer firms.

The final line deserves the closest scrutiny. Signing up 64,000 paying customers over five years works out to roughly 1,070 new customers every month on average, and that is before accounting for churn. When the startup's plan allows for only two salespeople and a modest advertising budget, such a SOM cannot be taken seriously. To correct it, the startup needs either to reduce the SOM or to provide a sales plan that explains where those customers will come from.

These are the default numbers in the calculator above, so you can change one input at a time and see how the result moves.

Where to find the numbers

• Business counts: the US Census Bureau’s County Business Patterns gives the number of establishments by industry code (NAICS), size and location. Eurostat publishes similar business statistics for EU countries, and most national statistics offices do too.
• Consumer counts: census population data by age, income and household type. Narrow it with survey data on who owns or uses the relevant product.
• Spending per customer: your own price, the prices of competitors, or spending surveys such as the Bureau of Labor Statistics Consumer Expenditure Surveys.
• Industry size: reports from industry associations, listed competitors’ annual reports, and analyst firms. Always note the year and the definition the report uses.

Common mistakes

• The “1% of a huge market” slide. “If we get just 1% of the $200 billion market” tells an investor you have not done the bottom-up work. Build SOM from customers and prices, not a percentage of a big number.
• Mixing up TAM and SAM. A US-only product with an English-only interface cannot claim the global market as its serviceable market.
• Using the wrong revenue per customer. TAM should use what customers would pay you, not their total spend in the category. A company that spends $20,000 a year on marketing does not spend $20,000 on your email tool.
• Mixing units. Keep everything in yearly revenue. A monthly price multiplied by a customer count gives a monthly figure, which makes the market look twelve times smaller than it is.
• Stale or unsourced figures. Put the source and year next to every number in your plan. Investors check.
• An SOM that the team cannot deliver. SOM should match your sales capacity and marketing budget. Divide it by revenue per customer and ask whether you can win that many customers.

What investors look for

Venture investors need companies that can grow very large, so they look for a TAM big enough to support a company worth hundreds of millions or more. A small TAM is not a problem for a profitable small business, but it will limit which investors are interested. What matters more than size is the logic: a clear, sourced bottom-up calculation, a SAM that shows you know your first segment, and an SOM that ties to your sales plan and your runway.

It also helps to show how the market expands. Many startups start with a narrow SAM, one country or one niche, and plan to widen it with new features, languages or customer segments. Showing that path makes a modest starting SAM look like a foothold rather than a ceiling.

Put your market size in your business plan

The market section of a business plan usually has three parts: the size of the market (TAM, SAM, SOM with sources), the customer segments you start with, and the trends that make the market grow. Your SOM should also line up with the revenue in your financial forecast. If your budget shows $2 million in revenue in year three, your SOM should make that look achievable.

Cuttles guides you through the market section step by step, next to your budget, so the market story and the numbers stay consistent. Once you know your costs, the break-even calculator shows how much of your SOM you need to win just to cover them. You can try the full app free for 7 days.

The calculator multiplies the numbers you enter. The quality of the result depends on the quality of your sources.