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Market size calculator

Write the equation first. Then punch the filters. Penetration and SAM are percents, not hidden decimals.

67,000,000 × 40% × 2 × $25 = TAM $1.34bn

TAM
$1.34bn
Everyone who could buy
SAM
$670.0m
50% of TAM — who you can serve
SOM
$134.0m
20% of SAM — who you can win

How to say it

Write the equation out loud. Then punch. TAM is population × penetration × frequency × price. SAM is who you can serve. SOM is who you can win.

Out loud
“UK-scale population, 40% penetration, two purchases a year, $25 ticket. TAM about $1.34bn. A 50% SAM and 20% reach puts SOM near $134m. Grocery-only is a SAM story. One in five accounts is SOM.”

Usual miss. Typing 40 into a 0–1 penetration field, or quoting eight digits with no sanity check.

Steal a prompt from market sizing questions, then time yourself in the market-sizing drill.

FAQ

What is TAM vs SAM vs SOM here?

TAM is the equation: population × penetration × frequency × price. SAM is the share of that universe you can actually serve (channel, geo, regulation). SOM is the share of SAM you can win. Both filters are editable. They were not meant to be a hidden 50%.

Should penetration be 40 or 0.4?

Type 40 for 40%. The old version asked for 0–1 and people typed 40, which blew the market by 100×.

When do I use this in a case?

After you write the equation out loud. The calculator is for the arithmetic. The case grade is the assumptions and the sanity check.

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