Total Addressable Market (TAM) is the yearly revenue available if every company that fits your ICP bought from you, and the formula is one line: TAM = number of ICP-fit accounts x average annual contract value. Count 150,000 accounts at a $10,000 ACV and the TAM is $1.5 billion. Your ACV is the easy input. The account count is where most TAM numbers go wrong, so most of this page is about getting that count right and checking it.
Key Findings
- The formula: TAM = ICP-fit accounts x average annual contract value. 150,000 accounts at a $10,000 ACV is a $1.5 billion TAM.
- Two methods. Top-down slices an analyst's market report and takes an hour. Bottom-up counts real companies and takes a day.
- The implied ACV test. Divide the top-down figure by your account count. If the spend per account it implies is over 2x your real ACV, the top-down number is measuring something else.
- TAM, SAM and SOM are three nested numbers. TAM is every fit account, SAM is the part you can serve today, SOM is what you can win in 12 to 18 months.
- Only the bottom-up number is usable by sales. It arrives as a list of named accounts, which is the same list an outbound campaign needs.
- Reachly runs a bottom-up TAM count across 10+ data sources at the start of every outbound engagement, then ranks the list by fit and buying signals.
What is Total Addressable Market?
TAM is the ceiling on revenue for your current product, price and ICP. It is the first of three market sizes, each one inside the last:
The number matters less than what you learn while counting it. Sizing TAM bottom-up makes you write down who your customer is in filters a database can run, and who it is not. A small TAM tells you early that pricing, the ICP or the market needs to change. A large one tells you to pick a first segment, because no team can work 150,000 accounts at once.
It also turns "the market" into a finite list of companies, which is where a repeatable sales motion starts. Reachly's founder's guide to outbound lead generation picks up from there.
What is the difference between TAM, SAM, and SOM?
TAM counts every account that fits. SAM takes out the accounts your business model cannot serve yet, such as countries you do not sell in or languages you do not support. SOM is the share of SAM you can realistically win in the next 12 to 18 months with the team and budget you have. Some guides write SAM as Serviceable Addressable Market; it is the same layer.
Here are the three layers for one illustrative project management software company selling at a $10,000 ACV:
| Layer | Who it counts | Accounts | Value |
|---|---|---|---|
| TAM | Companies worldwide with 50 to 500 employees in the industries the product fits | 150,000 | $1.5 billion |
| SAM | The ones in English-speaking North America, where the company sells and supports today | 60,000 | $600 million |
| SOM | The accounts the team can win in the next 12 to 18 months | 1,200 | $12 million |
Start with SOM, then use those first wins to expand across SAM. For the full SOM math, built from sending capacity and reply rates, see Reachly's TAM, SAM and SOM worked example for B2B outbound. To sharpen the segments themselves, read the modern guide to segmentation for B2B.
How do you calculate Total Addressable Market?
There are two methods. Top-down starts from a published market figure and narrows it with percentages. Bottom-up counts the companies that fit and multiplies by what each one pays. Run both, then use the check below to see which one to trust.
The top-down approach
Using the same project management software company:
- Start with a market report. Say an analyst report puts global spend on collaborative work management software at $60 billion.
- Apply your segment. You estimate companies with 50 to 500 employees make up 25% of that spend.
- Read the result. $60 billion x 25% = a $15 billion top-down TAM.
It takes an hour, and every step is an assumption. A small error in one percentage moves the answer by billions, and the report rarely matches the niche you actually sell into.
The bottom-up approach
- Count the companies that fit. Using a data tool like Clay or LinkedIn Sales Navigator, filter by the firmographics in your ICP. Say 150,000 companies worldwide match.
- Take your average annual contract value. Your average customer pays $10,000 a year.
- Multiply. 150,000 x $10,000 = a $1.5 billion TAM.
The number is smaller, and every unit of it is a named company you could contact tomorrow. Turning that list into meetings is the subject of Reachly's guide to sales prospecting techniques.
Check one against the other
The two answers above are ten times apart, and most guides stop there and tell you to average them. A better check takes one division: divide the top-down figure by your bottom-up account count. The answer is the yearly spend per account that the top-down number assumes. Compare it with your real ACV.
Over 2x apart: trust the account count, fix the assumption.
Here, $15 billion across 150,000 accounts assumes each one spends $100,000 a year, against a real contract of $10,000. The report is counting every tool and service in the category, so it is a ceiling for the whole space, not for your product. If the two numbers land within 2x of each other, your inputs are roughly consistent. Past 2x, keep the bottom-up TAM and go find the assumption that broke: usually a segment share that is too high, or a report that measures category spend.
How Reachly sizes a TAM for clients
When Reachly onboards a client, the first step is a bottom-up TAM count in Clay. Reachly pulls from LinkedIn Sales Navigator, Apollo and 10+ other data sources, dedupes the accounts, and keeps the ones that match the ICP agreed with the client. The list is then ranked by fit and buying signals. The output is an enriched account list ready for outreach, and the TAM figure falls out of it. Reachly's market mapping examples show what that list looks like once it is segmented.
Sizing a local or niche market
The same formula works for a local business. Count the businesses that fit in the area you serve, then multiply by the yearly value of a customer. In the US, the Census Bureau's County Business Patterns gives establishment counts by industry code and county, which is a free starting count before you check it against a data tool.
Which mistakes make a TAM calculation useless?
A bad TAM is worse than none, because it sets targets the team cannot hit.
Counting everyone in the industry
A company selling enterprise cybersecurity software to financial institutions might count every bank in the world. If the product needs a dedicated IT team and an enterprise budget, most small banks and credit unions were never buyers. Count only the accounts that pass every ICP filter, including price.
Using only top-down data
Analyst reports are a fine ceiling and a poor plan. A startup selling an HR tool to remote-first tech companies learns nothing from the size of the global HR software market. Run the implied ACV test above before a top-down number goes in a deck.
Ignoring who already owns the account
A new CRM cannot treat every business that needs a CRM as open. Many of those accounts are locked into contracts with an incumbent for years. TAM can include them, but SOM should not, and the outreach plan should start with the segments that are underserved.
How do you turn a TAM number into booked meetings?
A TAM is a spreadsheet until someone works the list. That is where most teams stall: they know who, and have no plan for how.
From account list to live targets
Reachly maps the market across 10+ data sources, then enriches every account with buying signals that show it may be looking now:
- Recent funding rounds: fresh capital usually means new budget for growth.
- Hiring trends: a run of sales or engineering hires points to expansion plans.
- Headcount growth: steady growth shows a business investing in its future.
- Tech stack changes: adding or dropping a tool signals a change in strategy.
From data and messaging to reply management
With the ranked list in place, Reachly runs coordinated campaigns through Smartlead for email and HeyReach for LinkedIn, alongside cold calling. Messaging is written around the signals on each account, and Reachly handles every reply, so the client's sales team joins only once a qualified meeting is on the calendar.
A mapped TAM also makes forecasting easier. Reachly's guide to 7 real-world examples of sales forecasting models that actually work shows how an account list turns into a revenue forecast.
Your TAM is a list of accounts. We work it.
Reachly maps your market across 10+ data sources, enriches every account with real buying signals, then runs cold email, LinkedIn and cold calling until qualified meetings land on your calendar.
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FAQ
Which is bigger, SAM or TAM?
TAM is always the bigger number, because SAM is TAM with the accounts you cannot serve yet taken out, and SOM sits inside SAM. If your SAM ever comes out larger than your TAM, the two were counted on different definitions, usually a TAM built on today's ICP and a SAM built on next year's product.
What does the acronym SOM stand for?
SOM stands for Serviceable Obtainable Market. You will also see SAM written as Serviceable Addressable Market instead of Serviceable Available Market. The two names mean the same layer, so pick one and use it the same way in every deck and plan.
What is a good SOM percentage?
There is no standard share worth aiming for. A SOM picked as a round percentage of SAM is a guess. Build it from capacity instead: how many accounts your team or campaigns can reach in the period, times the reply, meeting and close rates you actually see. The TAM, SAM and SOM worked example shows that math step by step.
How do you calculate market size?
Published market size is usually current spend across a whole category, including products you do not compete with. TAM is narrower: the revenue available to your product if every ICP-fit account bought at your price. That difference is why a category report and a TAM for the same space can be ten times apart.
Can you give me an example of TAM, SAM and SOM for a local business?
Take an illustrative bookkeeping firm that serves dental practices. TAM is every dental practice in the country times the yearly fee. SAM is the practices inside the states where it is licensed and can onboard clients. SOM is the number of new clients its team can take on in a year. The practice count comes from the Census Bureau's County Business Patterns, filtered by industry code and county.
How often should I recalculate my TAM?
A full bottom-up recount once a year, and a quick check each quarter. A price change, an ICP change or a new competitor all move the number, so rerun it whenever one of those happens rather than waiting for the calendar.
Does TAM include existing customers?
Yes. TAM is the whole opportunity, so the accounts you already serve sit inside it. Subtract current revenue from TAM to get the remaining opportunity, which is the more useful number for a growth plan.
Why do investors ask for TAM?
To check that the business can reach the revenue scale their fund needs. A TAM built from a named account list holds up better in that conversation than a percentage of an analyst report, because every assumption can be checked.
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