Total addressable market (TAM)

How total addressable market works

TAM measures how big the prize would be if every possible customer in the market bought the product. HubSpot defines it as the maximum potential demand of a specific market 1. The number is a ceiling. It ignores competition, reach and capacity, so it cannot stand in for a sales forecast.

The core formula multiplies a count by a price 2.

TAM = total potential customers x average annual revenue per customer

Carta uses average annual contract value, or AACV, for the revenue side 2. Its worked example sizes a product for public schools in the United States, starting from approximately 100,000 schools as the base number 2. If 10% of those schools would be interested, the TAM in customers is 10,000 2.

There are two ways to fill in the customer count 1.

• Top-down starts with total industry size from research reports, then applies percentage assumptions to reach the addressable slice 1.
• Bottom-up starts from data the team can observe, such as customer counts, pricing, sales metrics and conversion rates, and scales up 1.

Carta notes that top-down is often quicker but can be less accurate because it relies on estimates, while bottom-up takes longer and often gives more accurate results 2. HubSpot suggests running both and says a large gap between them signals areas that need deeper investigation 1.

For a B2B product, bottom-up usually means counting accounts. Write the ideal customer profile as filters, count the companies that match, and multiply by the expected contract value. Public statistics help with the count. The Statistics of U.S. Businesses series from the U.S. Census Bureau reports the number of firms and establishments by industry and enterprise size each year 3. Its latest data year is 2022, so treat it as a baseline rather than a live figure 3. Commercial B2B data adds filters the census does not have, such as firmographics beyond industry and size and the job titles of the people inside each account.

Where TAM estimates go wrong

Most weak TAM numbers fail in one of three places.

The first is the definition of a customer. A TAM built on every company in an industry counts businesses that could never buy, such as firms too small to need the product or too regulated to use it. Tie the count to ICP filters, especially headcount and region, and the number shrinks to something a sales team recognizes.

The second is the revenue side. Average revenue per customer should come from real pricing and signed deals. Carta frames it as average annual contract value 2. A list price that customers rarely pay inflates TAM by the size of the usual discount.

The third is presenting one method alone. HubSpot calls top-down analysis without bottom-up validation a common mistake and advises grounding the estimate in real customer data, pricing and unit economics 1. Investors look past the headline too. Carta notes they also want a realistic plan for capturing a significant portion of the market 2.

TAM is also not a sales target. The serviceable addressable market narrows it to what the company can reasonably target, and the serviceable obtainable market narrows it again to what it can potentially convert 1. Quotas and hiring plans belong to SOM.

A data index helps with the count but does not equal the market. A B2B database reports how many matching records it holds, which depends on its own coverage. Use that count to check reach inside the TAM, and use public statistics or several sources to check the TAM itself.

Example of a bottom-up TAM

A company sells a revenue operations tool to B2B software companies in Germany within one headcount band. The team sizes the market bottom-up. The figures below are illustrative.

Step 1  Accounts that match the ICP filters      4,000 companies
Step 2  Average annual contract value            EUR 6,000
Step 3  TAM = 4,000 x EUR 6,000                   EUR 24 million a year
Step 4  SAM = accounts the team can serve now     2,500 x EUR 6,000 = EUR 15 million
Step 5  SOM = share of SAM won in three years     10 percent of SAM = EUR 1.5 million

The account count in step one carries most of the risk, so the team checks it from two directions. A top-down figure from an industry report gives a rough range. A bottom-up count from company data gives the filtered number.

The team then checks reach inside the TAM, since a market the team cannot contact is not serviceable. A people search with the persona's job titles, the industry, the location and the employee size range returns a page of matches 4. The response field totalElements reports total matches for the filter set, and a page with limit 10 bills 1 credit 4. That count describes how many matching buyers one index holds, not how many exist. A count far below the account total, after allowing for several buyers per account, is a reason to add sources before the TAM goes into a plan, and it moves the SAM line down until the gap closes.

TAM vs SAM

HubSpot defines SAM as the size of the TAM a company can reasonably target as it builds its audience 1. TAM ignores the company's limits. SAM applies them, such as region, segment, language or product fit.