Market sizing estimates the total addressable market (TAM), the portion the product can serve (SAM), and the portion it can realistically capture (SOM). A top-down model applies serviceable and obtainable shares to a market estimate; a bottom-up model starts with customers and revenue per customer. PM Toolkit provides guided methods for both. Document the assumptions and time horizon behind each estimate.
What is TAM SAM SOM?
TAM (Total Addressable Market) is the total revenue opportunity available if a product achieves 100% market share. SAM (Serviceable Addressable Market) is the segment of TAM targeted by your products within your geographical reach. SOM (Serviceable Obtainable Market) is the portion of SAM you can realistically capture.
TAM SAM SOM Formulas
Top-Down TAM = Industry Revenue x Relevant Segment %
Bottom-Up TAM = Number of Target Customers x Annual Contract Value
SAM = TAM x Serviceable Segment %
SOM = SAM x Expected Market Share %
When to Use Market Sizing
Use TAM, SAM, and SOM for investor discussions, go-to-market planning, and resource allocation. Base obtainable share on the product, distribution, competition, and forecast period rather than a fixed percentage.
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Example
You size TAM 100M customers · $400 annual revenue/customer
pmtk → TAM = $40B
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Market Sizing Calculator
Calculate your Total, Serviceable Available, and Serviceable Obtainable markets — the foundation for fundraising and strategic planning.
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Total Addressable Market
Calculate the total revenue opportunity if you achieved 100% market share
Total Addressable Market
TAM represents the total demand for your product or service. Choose between top-down (using existing market data) or bottom-up (calculating from customer numbers) approaches.
Use existing market research data from analysts like Gartner or IDC. Best when reliable industry reports are available.
Calculate from customer segments and annual revenue per customer. Accuracy depends on the inputs.
To continue, fill in: Calculation Method, Number of Potential Customers, Average Annual Revenue per Customer
Understanding TAM, SAM, and SOM for Market Sizing
TAM, SAM, and SOM distinguish total market demand, the portion you can serve, and the share you estimate you can capture. They make the assumptions and constraints in a market estimate easier to inspect.
TAM vs SAM vs SOM: The Market Sizing Funnel
Total Addressable Market (TAM): The revenue opportunity under a broad market definition. You can estimate it with industry research or build a bottom-up model from customer segments.
Serviceable Available Market (SAM): The portion of TAM you can serve given geographic, regulatory, and technical constraints.
Serviceable Obtainable Market (SOM): The share of SAM you estimate you can capture, given competition, market conditions, and execution capacity. Treat it as an estimate of opportunity, not committed revenue.
Market sizing assumptions to document
- Method: Compare top-down and bottom-up estimates and explain the assumptions that produce each result.
- Capture: Set a SOM target that reflects the competitive alternatives, distribution plan, and execution capacity you can substantiate.
- Time horizon: State the period covered by the SOM estimate and the market-growth assumptions behind it.
- Constraints: Include geography, regulation, technical requirements, language, and payment coverage where they limit who you can serve.
- Updates: Refresh the model when material assumptions or target segments change.
Using market sizing in fundraising
A market-sizing model can show how a company defines its target market and what assumptions support its revenue opportunity. Investors and founders may weigh the market, growth, margins, distribution, and execution differently, so present the model as an estimate with a clear time horizon rather than a funding threshold.
Common Market Sizing Mistakes
Common errors include using global TAM for a product with regional limits, projecting market share without accounting for competitors and distribution, omitting accessibility constraints such as regulation or technical requirements, and assuming that new use cases will expand the market without evidence.
Rough Rules of Thumb for TAM→SAM→SOM
There's no published benchmark for how much of a market converts from TAM to SAM to SOM. The patterns below are directional rules of thumb, not measured figures, and your own numbers should come from your segments and constraints.
B2B SaaS: The relationship between TAM, SAM, and SOM depends on the target segment, contract value, buying process, and distribution model.
B2C/Consumer: Addressable reach, competitive intensity, and acquisition economics can all change the assumptions behind a SOM estimate.
Marketplace/Platform: Liquidity, supply and demand balance, and distribution costs are relevant assumptions to test when estimating obtainable share.
What is Market Sizing (TAM SAM SOM)?
Market sizing estimates a product’s revenue opportunity through TAM, the total addressable market; SAM, the portion you can serve; and SOM, the portion you expect to capture. The estimates help teams assess an opportunity and explain their growth assumptions.
TAM SAM SOM Formula
SAM = TAM × Serviceable %, then SOM = SAM × Obtainable Share %
Sizing assumptions
State the customer count, pricing basis, and reachable share behind the estimate; investor requirements vary.
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Review SAM and SOM alongside TAM. A large total market can include customers your product cannot serve or reach. Explain the customer segment, expected revenue, distribution limits, and time horizon behind the obtainable share.
Market sizing benchmarks by stage
| Segment | Benchmark |
|---|---|
| SaaS Startups (Seed) | SOM: $1-10M in 3 years |
| SaaS Startups (Series A) | SOM: $10-50M in 5 years |
| Growth Stage SaaS | Illustrative SOM: 1-5% of SAM |
| Market Leaders | Illustrative SOM: 15-30% of SAM |
Common questions
What is the difference between TAM, SAM, and SOM?
TAM (Total Addressable Market) is the total demand if you achieved 100% market share. SAM (Serviceable Available Market) is the portion you can realistically serve given constraints. SOM (Serviceable Obtainable Market) is the portion you can realistically capture given competition and execution capabilities. PM Toolkit's market sizing calculator walks you through each step with guided inputs.
How do you calculate TAM, SAM, and SOM?
Start with a market estimate supported by customer counts, spending data, or a relevant report. The wizard calculates TAM from market inputs, narrows it with serviceability filters for SAM, then applies market-share and execution assumptions for SOM. Its adjustment factors are model assumptions, not measured probabilities of capturing customers.
What is a good TAM size for venture capital funding?
There is no market-size cutoff that guarantees investor interest. State the customer population, spending assumptions, period, and share you could serve and capture. A large TAM does not show that your product can reach those customers or earn the projected revenue.
Should I use top-down or bottom-up market sizing?
Use top-down research to understand the broader market and bottom-up estimates to connect potential customers with spending. Compare their scope and assumptions when they disagree. Neither method is automatically more accurate; the quality of the inputs matters.
What are common market sizing mistakes to avoid?
Check for mismatched geography or time periods, unsupported capture assumptions, inaccessible customers, and double-counted segments. Distinguish current market size from future growth, and explain how competition and delivery capacity limit the share you could capture.
How does market sizing relate to product-market fit?
Market sizing estimates the opportunity under stated assumptions. Product-market fit concerns whether the product meets a need in a defined market. Neither calculation validates the other; compare the estimates with customer research, repeat use, and acquisition evidence.