SOM

The realistic share of the serviceable addressable market that a business can capture within a defined timeframe, given its current resources, competitive position, and growth trajectory.

SOM is the number investors and founders must be able to defend. It reflects grounded ambition: what can actually be won, not what theoretically exists. A credible SOM calculation demonstrates strategic thinking and market understanding.

A founder with a SAM of £120 million sets a three-year SOM of £3 million, representing 2.5% of her addressable segment. She supports this with her growth rate, conversion assumptions, and customer acquisition model, making it a defensible rather than aspirational number.