---
title: "Total Addressable Market (TAM): TAM vs SAM vs SOM, With Examples"
description: "Total addressable market (TAM), SAM and SOM defined, with a worked B2B example, the bottom-up formula, and how to turn your TAM into a scored account list."
url: https://getaob.com/total-addressable-market
---

# Total addressable market (TAM): TAM vs SAM vs SOM, with a worked B2B example

**Total addressable market (TAM)** is the revenue you would earn if every company that could use your product bought it. For a B2B company the honest version is a count: the number of accounts that fit your ICP, multiplied by what one of them pays you a year. SAM and SOM are smaller slices of the same count.

This guide covers the definitions, a worked example done both ways, and the bottom-up formula. To price what it costs to actually enrich that market, use the free [TAM calculator](https://getaob.com/tam-calculator).

By [Garrett Wolfe](https://garrettawolfe.com), founder of OneGTM, employee #9 at Unify, and author of the [State of GTME report](https://stateofgtme.com). Updated November 8, 2026.

Key takeaways

- TAM is everyone who could buy. SAM is the part your current product and team can serve. SOM is the part you can realistically win in a set period.
- Bottom-up TAM = accounts that fit your ICP × average annual contract value.
- Top-down numbers from analyst reports are fine for showing a category exists. They can't tell you who to call.
- A bottom-up count gives you a list as well as a number, and that list is where outbound starts.
- Total available market and total addressable market mean the same thing.

## TAM vs SAM vs SOM

The three terms nest inside each other. Each one answers a narrower question, and each one should come with an account count, not only a dollar figure.

| Term | The question it answers | How to count it | Typical use |
| --- | --- | --- | --- |
| TAM (total addressable market) | If every company that could use this bought it, how much revenue is there? | All accounts that fit the ICP, with no limits for region or integrations, × annual contract value | Fundraising decks, deciding whether a category is worth entering |
| SAM (serviceable addressable market) | How much of that can we sell to today? | TAM accounts that pass your current limits: regions, languages, integrations, compliance, deal size you can support | Territory planning, hiring plans, the target list for outbound |
| SOM (serviceable obtainable market) | How much can we actually win in the next one to three years? | SAM accounts you can reach and close with the team you have, usually capped by reps or by win rate | Revenue targets and the board plan |

You will also see **serviceable available market** for SAM and **serviceable obtainable market** or **share of market** for SOM. **Total available market** is another name for TAM. "Addressable market" on its own is loose, so when someone quotes one, ask whether they mean TAM or SAM. The [GTM glossary](https://getaob.com/gtm-glossary) has short definitions of these and the terms around them.

## The bottom-up TAM formula

| Market | Formula |
| --- | --- |
| TAM | Accounts that fit the ICP × average annual contract value (ACV) |
| SAM | Accounts you can serve today × ACV |
| SOM | The smaller of (SAM accounts × realistic win share) and (reps × deals per rep per year × years), × ACV |

If pricing varies a lot by company size, split the count into size bands and multiply each band by its own ACV, then add them up. One blended ACV across a 20-person shop and a 2,000-person company will mislead you in both directions.

## A worked B2B example, top-down and bottom-up

Say you sell scheduling and dispatch software to US home services contractors (HVAC, plumbing, electrical) with 10 to 200 employees, at about $6,000 a year per company. The numbers below are made up to show the method. Swap in your own.

### Top-down

You find an analyst report that sizes the global field service software market at $5B. You assume you can take 1% and call your market $50M. The math is quick and it looks fine in a deck, but nothing in it can be checked. The report's definition of the category may include enterprise utilities you will never sell to, and the 1% is a guess with nothing under it.

### Bottom-up

1. **TAM:** you count about 60,000 US contractors in those trades with 10 to 200 employees. 60,000 × $6,000 = **$360M** a year.
2. **SAM:** today you support 12 states and only integrate with QuickBooks. About 18,000 of those contractors pass both limits. 18,000 × $6,000 = **$108M**.
3. **SOM:** you have four account executives who can each close about 40 deals a year. Over three years that is 480 accounts, or about 2.7% of SAM. 480 × $6,000 = **$2.9M** in annual recurring revenue.

The bottom-up version gives a smaller headline, and it is the one an investor can test. Ask how you got to 60,000 and you can show the filters and the source. It also tells you something useful: SAM is less than a third of TAM, so adding states and a second accounting integration grows the serviceable market faster than hiring more reps would.

Want this built for your team?

Tell me what you're trying to fix. The call is with me, and I'm the one who'd build it.

Book a call with Garrett

## Why bottom-up account counts beat analyst reports for a startup

Analyst reports size categories for large vendors and investors. Their definitions are broad and the method usually sits behind a paywall. A dollar figure also gives a sales team nothing to act on. A startup needs to know which companies to sell to this quarter.

A bottom-up count fixes that. The ICP becomes a set of filters a database can check, and every assumption is written down where someone can argue with it. When the ICP changes, you rerun the filters and the number moves with it. Most of all, the list you used to size the market is the same list sales works from, so the TAM doubles as the target list.

There is one trap. Company databases miss plenty of businesses, especially small, local and non-tech ones that barely exist on LinkedIn. If your buyers look like that, count from public sources too: state licensing boards, provider registries, permit filings, Google Maps listings. The [data enrichment tools](https://getaob.com/data-enrichment-tools) guide covers where each kind of record comes from. And if the official count comes from government data, the US Census Bureau's [Statistics of US Businesses](https://www.census.gov/programs-surveys/susb.html) publishes firm counts by industry and employee size, which is a good sanity check on your database's number.

## How to build a TAM list you can sell to

1. **Write the ICP as filters.** Industry codes or keywords, employee band, region, and anything else a machine can check, such as a technology on the site. The [GTM strategy guide](https://getaob.com/gtm-strategy) covers how to choose them.
2. **Pull from more than one source.** A firmographic database plus whatever public records cover your buyers. Expect each source to miss companies the others have.
3. **Dedupe on domain.** The same company shows up under several names. Without this step, your TAM is inflated.
4. **Qualify each account.** Filters are blunt. Reading each company's website with an AI model catches the ones whose industry code says plumbing but who only sell fixtures.
5. **Score what is left.** Rank accounts on fit, then check the distribution. If most accounts land on the same score, the model isn't separating anything.
6. **Add signals for timing.** Fit says who. [Buying signals](https://getaob.com/buying-signals) such as hiring, funding or a new leader say when.

Then price it. Enriching every account and finding verified contacts costs real money at TAM scale, and it is easy to underestimate. The [TAM calculator](https://getaob.com/tam-calculator) works out that line from current vendor rates.

## How OneGTM builds a TAM for outbound

At OneGTM the TAM is the first thing I build in an engagement, in the first two weeks while sending domains warm up. It is every account that fits, pulled from several sources, deduped, qualified and scored, and the client reviews that snapshot before any list goes into a campaign. The rest of the [GTM playbook](https://getaob.com/gtm-playbook) works off that list.

For one vertical SaaS client with a TAM of about 45,000 companies, rebuilding the scoring model moved the median score from 0.25 to 0.50 and left 2,001 accounts above 0.75. That top tier is what the team worked first. The market isn't always a list of companies, either. For [Green Dock Partners](https://getaob.com/green-dock-case-study), a private equity firm buying industrial real estate, the market was sites, so the tracker counts 518 industrial sites from public closure news and ranks the top ones for calls.

## Total addressable market FAQ

### What is total addressable market (TAM)?

Total addressable market (TAM) is the annual revenue you would earn if every company that could use your product bought it at your price. For a B2B company, the clearest way to state it is the number of accounts that fit your ICP multiplied by your average annual contract value.

### What is serviceable addressable market (SAM)?

Serviceable addressable market (SAM), also called serviceable available market, is the part of your TAM you can actually sell to today with your current product, regions, languages, integrations and sales motion. Count the accounts that pass those limits and multiply by your annual contract value.

### What is the difference between TAM, SAM and SOM?

TAM is everyone who could ever buy. SAM is the share of TAM your current product and team can serve. SOM, the serviceable obtainable market, is the share of SAM you can realistically win over a set period, usually limited by sales capacity and competition.

### Is total available market the same as total addressable market?

Yes. Total available market and total addressable market are used as synonyms, and both shorten to TAM. Some people use addressable market on its own to mean either TAM or SAM, so say which one you mean when you quote a number.

### How do you calculate TAM bottom-up?

Write your ICP as filters (industry, employee band, region, technology), count the companies that pass them in a company database or public registry, then multiply that account count by your average annual contract value. Repeat with tighter filters to get SAM.

### Should a startup use a top-down or bottom-up TAM?

Bottom-up. A top-down number from an analyst report shows the category exists, but it cannot be checked and it does not tell your team who to call. A bottom-up count of real accounts can be checked by an investor, and the same list becomes your outbound target list.

Want your TAM built as a scored list instead of a slide?

## Related

- [TAM calculator](https://getaob.com/tam-calculator): Estimate what it costs to enrich your TAM: firmographics, AI site reads, signals, contacts and verified emails, priced from real vendor rates.
- [Free B2B lead lists](https://getaob.com/lists/): Free lists of US and Canadian companies by industry, each with a 1,000-row CSV download.
- [Ideal customer profile (ICP) guide](https://getaob.com/ideal-customer-profile): What an ICP is in B2B, ICP vs buyer persona, how to build one from closed-won data, a fill-in template, and a worked example.
- [GTM strategy guide](https://getaob.com/gtm-strategy): How to build a B2B go-to-market strategy, with worked examples, a one-page template, and a 90-day test plan.
- [GTM playbook](https://getaob.com/gtm-playbook): A practical go-to-market checklist for B2B startups, from ICP and signals to outbound, routing, and measurement.
- [Buying signals guide](https://getaob.com/buying-signals): The 15 B2B buying signals worth tracking, how to detect each one, and how to turn a signal into outreach.
- [Best data enrichment tools](https://getaob.com/data-enrichment-tools): The enrichment stack OneGTM runs, plus the main alternatives and what each costs.

## Talk to OneGTM about building your TAM

Tell me what you're building. I reply the same day.

Book a call at [getaob.com/#contact](https://getaob.com/#contact) or email [team@getaob.com](mailto:team@getaob.com).