Market Sizing Model: TAM, SAM, SOM with Top-Down and Bottom- – Excel XLSX

Most market sizing models pick one construction and hope. This eleven-tab workbook builds the market twice and makes you resolve the difference.
The top-down cascade runs from a sourced parent market through a scope fence to current penetration, one step per row. The bottom-up build multiplies units by realised value across four segments and tests for double counting rather than assuming it away. The two are compared against a stated tolerance, and the model records which construction the published figure rests on. Divergence is investigated, never averaged away.

On top sit a TAM to SAM to SOM bridge with every narrowing constraint named and quantified, a five-year segment forecast, a three-scenario comparison from one engine, a two-way sensitivity grid, and a dashboard of figures and native charts to lift into a deck.

It starts where a defensible sizing has to start: scope, exclusions, customer, geography, base year, currency basis and unit are all required, because a size without a scope fence is not a number. The source register keeps a sourced fact, a third-party estimate and your own judgement in separate tiers.

A modelling framework – figures shipped are illustrative.