Market Sizing
TAM, SAM, and SOM by triangulation, delivered as defensible ranges, not applause numbers.
A market size is an estimate, and estimates deserve error bounds. We size markets three independent ways, top-down decomposition, bottom-up unit build, and demand-side construction, then reconcile the disagreements, because the disagreements are where the insight is. The output survives diligence because it shows its work.
Who this is for
Founders raising or planning, and investors validating the number on slide four.
How the work is done
Define the unit of demand
What exactly is bought, by whom, how often, at what price, a Fermi decomposition of demand that forces every assumption into the open before any multiplication happens.
Triangulate three ways
Top-down: authoritative aggregates decomposed with explicit filters. Bottom-up: buyer counts × adoption × frequency × price, built from primary data where possible. Demand-side: budget or time displaced. Three estimates, independently constructed.
Reconcile and bound
Where the methods disagree we find out why, usually a hidden assumption, and express the final size as a range with a stated confidence level. Monte Carlo on the key parameters produces honest intervals instead of false precision.
Forecast adoption
For growth markets, Bass-diffusion and S-curve logic model penetration paths under different innovation/imitation assumptions, with the parameters benchmarked to analogous historical adoptions.
How the Market Sizing engagement runs
We begin with the decision, use the evidence that can genuinely change it, and make the reasoning reviewable from first input to final handover.
What we need to begin
- The unit of demand to be sized (users, seats, transactions, spend) defined precisely enough to count.
- The geography, segment, and time horizon in scope.
- Prior sizing attempts, including ones the client rejected, and the reason they were rejected.
- Internal demand data (pipeline, sales history, usage) that can anchor a bottom-up build.
If an input is unavailable, we state the gap, its effect on confidence, and the agreed workaround. It is never quietly ignored.
Your four-phase engagement map
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Phase 1
Define the unit of demand
A Fermi decomposition of what is bought, by whom, how often, at what price, forcing every assumption open before any multiplication.
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Phase 2
Triangulate three ways
Top-down decomposition, bottom-up unit build, and demand-side construction, independently.
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Phase 3
Reconcile and bound
Find why the methods disagree and express the size as a range with a confidence level; Monte Carlo the key parameters for honest intervals.
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Phase 4
Forecast adoption
Model penetration with Bass and S-curve logic, benchmarked to analogous historical adoptions.
Methods and models we draw on
- Fermi decomposition
- Top-down / bottom-up / demand-side triangulation
- TAM–SAM–SOM discipline
- Monte Carlo uncertainty intervals
- Bass diffusion forecasting
- Analogous-adoption benchmarking
Methods are chosen for the problem, not the brochure, expect a subset of these, applied properly, plus whatever the evidence demands.
The decision this enables
A market size you can defend to a sceptical investment committee, with the reasoning visible.