BMS5502S Chap.6 Sizing the Market from TAM to SOM
Sizing the Market from TAM to SOM
Why a founder sizes a market
The second of the three opportunity tests asks whether a market is large enough to build a business. The course's learning outcomes name quantitative market sizing with TAM, SAM and SOM, and the first project rubric distinguishes data-driven sizing based on credible Singapore sources from a generic global figure. Sizing is therefore not a slide to decorate a pitch.
It is an argument about how much revenue a specific venture could realistically earn.
Three nested measures
The total addressable market counts everyone who could in principle need the solution, multiplied by what they spend on the category.
The serviceable addressable market is the slice of that total the business model is able to reach and deliver to, narrowed by geography, customer profile and delivery limits. The serviceable obtainable market is the share the venture can realistically capture within three to five years given competition and resources.
The session suggests where the data comes from: national statistics, industry reports and market research databases for the outer measures, and pilots, pre-orders, landing-page tests, acquisition cost and operating capacity for the inner one.
Top down and bottom up
The outer measures are usually built top down, starting from a market total and applying filters.
The session insists that the obtainable market should be built bottom up from unit economics, meaning average revenue per customer multiplied by the number of customers the venture can actually reach, or for a marketplace the number of orders its partners and capacity can handle multiplied by order value and the platform's share.
Its key insight is that SOM is worked out from what partners and operations can handle, not guessed as a percentage of a large number.
A deck that claims one per cent of a huge market has assumed its answer.
Size is read with other dimensions
The session lists further dimensions for analysis: growth trajectory, separating structural from cyclical or inflated growth; maturity stage; geographic concentration; demographics of who suffers the problem, who funds the purchase and who sways it; the macro forces of PESTEL; and structural dynamics such as barriers to entry.
It notes that the richest insights come from intersections between these dimensions.
Four lifecycle stages
Markets are described as emerging, growing, mature or declining. Emerging markets demand heavy customer education and carry the risk that demand never appears. Growth markets let acquisition costs fall but tempt ventures to scale before product-market fit.
Mature markets compete on price and features and risk disruption from adjacent markets. Declining markets are harvested. The session adds that the same category can be at different stages in different countries.
What this chapter covers
- 01
TAM, SAM and SOM defined with typical data inputs
- 02
Top-down filters for the outer measures
- 03
Bottom-up SOM from capacity, order flow and take rate
- 04
Growth, maturity, geography and demographics as further dimensions
- 05
Emerging, growth, mature and declining markets
- 06
Geographic variation in lifecycle stage
Worked example · free
A bottom-up SOM for a tutoring marketplace
- 3Compute annual lesson value from capacity.
- 2Apply the platform share to get SOM.
- 1Comment on what drives the result.
Key terms
- Total Addressable Market
- Everyone who could in principle need a solution, multiplied by annual spending on the category.
- Serviceable Addressable Market
- The portion of the total market a venture's business model can actually reach and serve.
- Serviceable Obtainable Market
- The revenue a venture can realistically capture in three to five years, built from its capacity.
- Bottom-Up Sizing
- Estimating revenue from unit economics and reachable customers rather than from a share of a total.
- Take Rate
- The share of each transaction a platform keeps as its revenue.
- Market Lifecycle
- The progression of a market through emerging, growth, mature and declining stages.
Sizing the Market from TAM to SOM FAQ
What is the difference between TAM, SAM and SOM?
TAM counts all potential demand for the category, SAM narrows it to the part the business model can serve, and SOM estimates what the venture can realistically win within a few years given its resources and competition. Each is smaller than the one before because each applies a real limit.
Why should SOM be built bottom up?
A share of a large total is an assumption that cannot be checked. A bottom-up figure multiplies things the team can evidence, such as partners, orders per day, order value and take rate, so it can be tested and improved. The session calls this far more credible than a top-down share.
Where does a Singapore project find sizing data?
The session points to the Singapore Department of Statistics and census data, industry reports and market research databases for the outer measures, and to pilots, pre-orders, landing-page tests and operating capacity for the obtainable market. The first project rubric rewards Singapore-specific figures.
How does market maturity affect a startup's entry?
Emerging markets require expensive customer education, growth markets reward speed but punish scaling before product-market fit, mature markets compete on price, and declining markets are harvested. The stage tells a founder what entry will cost and which risk to plan around.
Can a small SOM still be a good opportunity?
Yes, if it is honestly derived and supports a viable business. A small, evidenced figure is more useful than a large assumed one. The test is whether realistic customers, price and margin add up to a business worth building.
Exam move
Size one market three times, first with a guessed share, then top down with filters, then bottom up from capacity, and compare the answers. Seeing how far the guessed share drifts from the capacity figure makes the session's key insight stick.
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