Strategy
Build a bottom-up TAM, SAM and SOM from company counts and ACV.
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- Claude, via MCP
How do you calculate TAM, SAM and SOM?
Bottom-up, TAM = number of companies that fit your customer profile × average annual contract value. SAM = TAM × the share of those companies you can actually reach and serve today. SOM = SAM × the market share you can realistically win in the next two to three years. Plan budgets and hiring against SOM, not TAM.
Bottom-up, your near-term obtainable market (SOM) is about $20,160,000, that’s the number to plan and pitch against. TAM ($1,440,000,000) is the ceiling story; SOM is what your GTM can actually credibly capture.
Bottom-up TAM (company count × ACV) survives investor scrutiny far better than top-down "1% of a $50B market" hand-waving.
About this calculator
Most TAM slides are top-down guesswork, "the industry is $50B, we just need 1%", and investors have heard that pitch enough times to discount it on sight. This estimator builds the number from the ground up: how many companies actually fit your target profile, how many of those you can realistically reach, and what each is worth, so the market-size story survives real diligence.
How to use it
- Enter total target companies, the full count of organizations that fit your ideal customer profile, by industry, size, or geography.
- Enter the percentage realistically reachable, the share you can serve given your current geo, segment focus, and go-to-market motion.
- Enter average contract value, what a typical customer actually pays per year.
- Enter obtainable market share, the percentage of your serviceable market you can credibly capture in the near term, and read TAM, SAM and SOM.
Methodology
TAM (Total Addressable Market) is the full ceiling: total target companies × average contract value. This is the entire theoretical market if you sold to everyone who could conceivably buy.
SAM (Serviceable Addressable Market) narrows that to companies you can actually reach: total companies × reachable percentage × ACV. This accounts for geography, segment, language, or product-fit constraints that TAM ignores.
SOM (Serviceable Obtainable Market) narrows further to what you can realistically win near-term: SAM × your target market share percentage. This is the number a credible go-to-market plan should be built against.
The gap between TAM and SOM is deliberate and large by design, TAM is the story for why the category matters, SOM is the plan for what your specific GTM motion can capture given today's constraints.
Bottom-up TAM, SAM and SOM formulas
TAM = Target companies × Average contract value SAM = Target companies × Reachable share × Average contract value SOM = SAM × Obtainable market share Implied customers at SOM = Target companies × Reachable share × Obtainable market share
- Target companies
- Count of organisations that match your ideal customer profile (industry, size, geography), from a source you can show.
- Average contract value
- What a typical customer pays per year, after discounts. Use annual value, not lifetime value.
- Reachable share
- Percentage of target companies your product, language, geography and sales motion can serve today.
- Obtainable market share
- Percentage of SAM you can credibly win in the planning horizon, usually two to three years.
The tool shows TAM, SAM and SOM; the last line above is not displayed but is worth working out by hand, because a SOM of ₹20 crore at a ₹3 lakh ACV means roughly 667 customers, and your sales team has to be able to win that many. The method assumes one contract per company. If large customers buy several seats, products or regional contracts, ACV should reflect total annual spend per company. Bottom-up sizing describes the market as it exists. Bill Gurley argues that the past can be a poor guide when a new product changes what customers can do, so a genuinely new category may be larger than today's count suggests; say so explicitly rather than inflating the inputs.
Worked example: an Indian B2B SaaS product for mid-size companies
An HR software company filters a company database to 60,000 Indian companies in its target size band and sectors. Its product is English-only and the sales team covers six metros, so it can serve about 40% of them. Average contract value is ₹3 lakh a year. Leadership believes a 3% share of reachable companies is achievable in three years.
- TAM = 60,000 × ₹3,00,000 = ₹18,00,00,00,000 = ₹1,800 crore
- SAM = 60,000 × 0.40 × ₹3,00,000 = 24,000 × ₹3,00,000 = ₹720 crore
- SOM = ₹720 crore × 0.03 = ₹21.6 crore
- Implied customers at SOM = 24,000 × 0.03 = 720 customers
- Capacity check: if each account executive wins about 40 new customers a year, 720 customers over three years needs about 6 fully productive reps (720 ÷ 3 ÷ 40)
The ₹1,800 crore TAM explains why the category matters; the ₹21.6 crore SOM is the number to build the plan around. Converting SOM into 720 customers makes it testable against sales capacity and pipeline. If the team cannot win roughly 240 customers a year, either the share assumption or the hiring plan has to change. Adding Hindi support or tier-2 coverage would raise the reachable share and SAM without changing TAM.
What makes a credible TAM?
A credible TAM is one a sceptical reader can rebuild from your inputs. Size is secondary to traceability:
- Company count from a named source. Government business registers, a commercial database export with filters listed, or your CRM. For the US, the Census Bureau's Statistics of U.S. Businesses tables report firm counts by NAICS industry, state and enterprise employment size.
- ACV from real deals. Use the median of closed-won contracts, not list price, and state whether it includes implementation fees.
- Reachable share tied to a constraint. Write down why the other companies are out of reach (language, geography, integrations, deal size), so each constraint can be removed later. Reachable and obtainable shares are planning assumptions, not measured benchmarks, so their credibility comes from the constraints and capacity behind them.
- SOM checked against capacity. Implied customers ÷ years should be close to what the sales team can win; the sales quota calculator helps with that check.
A decision rule: if SOM requires more new customers a year than your pipeline and team can produce, the SOM is a target, not a forecast. Use the annual growth goal back-calculator to turn it into pipeline numbers, and the ICP and buyer persona template to define who counts.
Market sizing in India vs the US
India has a large count of registered companies but a much smaller active base: the Ministry of Corporate Affairs bulletin reported 28,96,943 registered companies as on 31 May 2025, of which 18,90,305 (65%) were active (IANS via Siasat). Start from active companies, then filter by size and sector, because many registered entities never trade. Proprietorships and partnerships that sell to consumers are not in the company register at all, so for SMB products combine sources such as GST registrations or Udyam MSME data. ACVs in rupees are usually lower than US ACVs for the same software, so an India TAM often looks small in dollars; present it in crore and alongside customer counts. The go-to-market consultant for India page covers how entry plans are usually sequenced.
US market sizing usually starts from Census Bureau firm counts, which are published by NAICS industry, geography and enterprise employment size in the SUSB tables, then narrows with a commercial database for technology use or funding stage. The 2022 SUSB tables were last revised on 4 August 2025 and use 2017 NAICS codes, so match your industry definitions to that version. Because US ACVs are higher, small changes in the reachable share or obtainable share move SOM by large dollar amounts; show a range rather than a single figure. Companies comparing several countries can rank them with the internationalisation market prioritisation grid.
Common TAM, SAM and SOM mistakes
- Starting from an analyst report figure for a whole industry and taking a percentage of it, which mixes buyers and products you do not sell to.
- Using lifetime value or multi-year contract value as ACV, which inflates TAM by the contract length.
- Counting all registered companies instead of active ones, or counting subsidiaries and parent companies separately when they buy once.
- Setting reachable share without naming the constraint, so no one can tell whether 35% is cautious or generous.
- Presenting a SOM that implies more new customers a year than the sales team and pipeline can produce.
- Converting INR to USD at one rate in the deck and another in the model, or mixing currencies within ACV.
Sources
- 2022 SUSB Annual Data Tables by Establishment Industry, U.S. Census Bureau. Accessed 2026-10-17.
- India sees 29 pc surge in new company registrations in May, Siasat Daily (IANS), reporting the Ministry of Corporate Affairs monthly bulletin. Accessed 2026-10-17.
- How to Miss By a Mile: An Alternative Look at Uber's Potential Market Size, Above the Crowd (Bill Gurley). Accessed 2026-10-17.
FAQ
A bottom-up number, built from company counts and a real ACV, gives an investor or exec something they can independently sanity-check: is that company count right, is that ACV realistic. A "we just need 1% of a $50B market" claim gives them nothing to verify, which is exactly why it gets picked apart.
Be honest about constraints your GTM actually has today, language, region, company-size fit, channel reach. A 20-40% reachable share is a common planning assumption for a focused early-stage motion, not a measured benchmark, so tie whatever figure you use to named constraints. Claiming 80%+ reachable usually signals the ICP definition is too loose.
Single digits, often 1-5% of SAM within a 2-3 year horizon, is a common planning assumption for a competitive category, not a measured benchmark; check it by converting SOM into a customer count your sales team can actually win. Double-digit share claims need a specific reason: a category with few incumbents, a strong existing wedge, or genuine first-mover advantage.
SOM. It reflects what your actual GTM engine can capture given today's constraints. TAM and SAM are useful for framing category size to investors, but planning headcount or spend against them invites the kind of overreach that burns cash chasing a market you can't yet touch.
Combine a public register with a filtered database. In India, start from active companies in the Ministry of Corporate Affairs data, then narrow by size and sector; in the US, Census Bureau SUSB tables give firm counts by industry and employee size. Then filter with a commercial database or your CRM for the attributes that define your ICP.
Yes, in this method it is annual: companies × annual contract value. Keep SAM and SOM on the same annual basis, and if you quote a three-year SOM, say whether it is annual revenue in year three or cumulative revenue.
Replace companies with households or individuals who fit the buyer profile, and replace ACV with expected annual spend per customer (average order value × orders per year). Reachable share then reflects delivery coverage, price fit and channels you can access.
Top-down starts from a total industry figure and narrows it by percentages. Bottom-up, as in this calculator, multiplies a counted set of buyers by a real price. Bottom-up is easier to check; top-down is useful as a cross-check that the bottom-up number is in a plausible range.
Include it only if you sell it and it recurs or is part of a typical first-year contract. Many SaaS companies size TAM on subscription ACV alone and show services separately, which keeps the number comparable with recurring revenue metrics.
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