TAM SAM SOM calculator: size your market from the bottom up

A TAM SAM SOM calculator multiplies the number of possible customers by what each pays a year (TAM), keeps only the share you can actually serve (SAM), then takes the share you can realistically win (SOM). This one builds the numbers bottom-up from company counts, and adds a check most calculators skip: whether your sales team can close that many customers in the time you gave it.

How to use the TAM SAM SOM calculator

Start with a count of real buyers. Enter how many companies (or people, if you sell to consumers) could ever buy what you sell, and what one of them would pay you in a year. Then add up to three filters for the part of the market you can serve today: the regions you sell in, the company sizes you fit, the tools they must already use. Each filter is the share that passes it. Last, enter the share of that market you expect to win, over how many years, and how many new customers your salespeople close a month.

The result updates as you type. Copy summary gives you a plain-text block you can paste into a plan, a pitch deck or an email to a co-founder.

How TAM, SAM and SOM are calculated

The tool uses the bottom-up method: count the buyers and multiply by price. The top-down route, taking a slice of a big industry figure, hides the assumptions that decide the answer. Counting buyers puts them in plain view. Here is every formula it applies:

TAM = companies in the market x revenue per customer per year
Serviceable share = filter 1 % x filter 2 % x filter 3 %
SAM customers = companies x serviceable share
SAM = TAM x serviceable share
SOM customers = SAM customers x share you expect to win
SOM = SAM x share you expect to win

Months = years x 12
New customers needed a month = SOM customers / months
Sales capacity = salespeople x customers each closes a month x months
Plan on = the lower of SOM customers and sales capacity
Plan-on revenue = plan-on customers x revenue per customer

SOM here is yearly revenue once those customers are won and still paying. If you lose customers along the way, the real figure will be lower, so treat it as a ceiling for the period.

Where to get the company count

For US business markets, the Census Bureau publishes two free sources. County Business Patterns gives the number of establishments with paid employees by industry (NAICS code), county and employee size class. Statistics of U.S. Businesses gives the number of firms by industry and enterprise size. Firms and establishments are not the same thing: a chain with 40 branches is one firm and 40 establishments. Count the unit that signs your contract. To look up the right industry code, use the Census NAICS search.

If you sell to named accounts rather than a whole industry, a real list beats any estimate. Pull the companies that match your filters, count the rows, and use that as SAM directly by entering 100 in one filter.

Worked example: a B2B tool sold to small firms

These are example numbers, not real market data. They are the values filled in above.

Market: 120,000 companies, each worth $4,800 a year
TAM:  120,000 x $4,800 = $576,000,000

Filters: regions you sell to 50% x company size you fit 50% = 25%
SAM:  120,000 x 25% = 30,000 companies
      $576,000,000 x 25% = $144,000,000

Win 2% of SAM over 3 years
SOM:  30,000 x 2% = 600 customers
      600 x $4,800 = $2,880,000 a year

Needed: 600 / 36 months = about 16.7 new customers a month
Capacity: 2 salespeople x 4 a month x 36 months = 288 customers
Plan on: 288 customers x $4,800 = $1,382,400 a year
To reach 600: 16.7 / 4 per person = 5 salespeople (rounded up)

The share-based SOM says $2.88 million. The team can close less than half of that in three years. That gap is the most useful number on the page: either the plan needs more people, a faster sales cycle, or a smaller target.

What a good TAM SAM SOM looks like

A number investors or a board will trust has three things. Every input can be traced to a source or a list. SAM filters describe real limits, such as a language you do not support or a company size you cannot serve. And SOM matches what the team can do. If your SOM needs more new customers a month than your team has ever closed, treat it as a hope until you hire or speed up the sales cycle.

Some checks before you use the number:

• Your revenue per customer is what customers pay now, not a future price.
• Each filter is a separate question. Do not count the same limit twice.
• The count uses one unit throughout: firms, sites or people.
• You can name where each figure came from if someone asks.

What to do next

Turn SOM into a pipeline. If you need 16.7 new customers a month, work back through your reply, meeting and close rates to find how many prospects you must reach. The lead generation cost reality check shows what that pipeline costs to fill, and the lead scoring calculator helps you rank which of the SAM accounts to call first. To see how your market splits between you and the players already in it, try the AI competitor gap analyzer.

When you are ready to reach the companies in your SAM, you need them as a list with a named person and a work email for each. Our page on how Verified B2B Leads works explains how that list is built from the filters you used here.

Questions people ask

How do you calculate TAM, SAM and SOM?

Multiply the number of possible customers by what one pays a year to get TAM. Multiply TAM by the share you can serve, based on filters such as region and company size, to get SAM. Multiply SAM by the share you expect to win in a set period to get SOM. For example, 120,000 x $4,800 = $576 million TAM.

What is the difference between TAM, SAM and SOM?

TAM is the total addressable market: everyone who could buy what you sell. SAM is the serviceable addressable market: the part you can reach with your product, regions and sales channels today. SOM is the serviceable obtainable market: the part you can realistically win in a set time. Each one is a slice of the one before.

What is a realistic SOM percentage?

There is no standard figure, because it depends on your price, your competitors and your sales team. A better test is capacity: divide SOM customers by the months in your plan and compare that with how many new customers your team actually closes a month. If the SOM needs more than that, plan on the lower number.

What is bottom-up market sizing?

Bottom-up market sizing starts from a count of real buyers and multiplies by the price each pays. Top-down sizing starts from a total industry figure and takes a percentage of it. Bottom-up is easier to check, because every input is a count or a price you can source, and it shows exactly which assumption moves the result.

Where can I find the number of companies in my market?

For US markets, the Census Bureau's County Business Patterns gives establishment counts by industry code, county and employee size class, and Statistics of U.S. Businesses gives firm counts by industry and company size. Look up your industry code with the Census NAICS search first. For a named-account market, a filtered company list is more accurate than either.