TAM, SAM, SOM
Three letters that get founders into more trouble than any others. TAM, SAM, SOM — total, serviceable, obtainable. Three different numbers with three different meanings, and most pitches confuse them in the first 30 seconds.
Here's the trick: a panel hears TAMand assumes you're going to say something stupid. Founders quote a $500-billion market and act like they're going to capture all of it. Nobody captures all of it. ServiceNow, the most successful enterprise software company of the last decade, has $4B of ARR in a market they pegged at $200B+ — that's a 2% capture rate, and they're considered a generational outcome.
▸ The three numbers, plain English
Every dollar that could theoretically be spent on this category, anywhere on earth. The big sexy number. Useless on its own — the panel only cares about it as a sanity check that the category isn't tiny.
The slice of TAM you can actually reach with your product, geography, and channel. India only? B2B only? English-speaking only? SAM is what's left after the filters.
The slice of SAM you can realistically capture in 5 years. This is the only number the panel actually underwrites against — your revenue plan rolls up to SOM, not TAM.
The classic mistake
"Our TAM is $500 billion. If we capture even 1%, that's $5 billion in revenue." Every panel has heard this sentence five times this week and rolled their eyes five times. The 1% capture rate is doing all the work — and the founder hasn't shown why their 1% is more likely than the 1% of the next four founders this week. Drag the numbers below and see how SOM behaves when the math is honest.
▸ If you had this TAM and this realistic capture rate, what's your SOM?
$50B TAM × 1% = $500M of revenue you could plausibly own. That's a real venture-scale outcome.
A founder says: 'Our TAM is $200B. We're going after the SOM, which is the $40B of US enterprise customers.' What's wrong?