Serviceable Obtainable Market (SOM)

What it actually means

SOM sits at the bottom of the TAM, SAM, SOM stack. TAM is the total theoretical demand for what you sell. SAM narrows that to the segment you can actually serve given your product and geography. SOM narrows it again to what you can win in a realistic window, usually the next one to three years, given your headcount, your budget, and who else is already selling into that segment.

So if TAM is "every company that could use this category of product" and SAM is "every company that fits our ICP and region," SOM is "the number of those companies we can actually close given our current sales team, our win rate, and the fact that three competitors are already in those accounts."

Why it matters when you're selling

TAM and SAM are useful for investors and for sizing a category. SOM is the number that should actually drive your quota, your headcount plan, and your pipeline targets. If your SOM this year is 200 accounts and your rep can realistically work 40 accounts through a cycle, you need five reps, not two. A lot of bad quota math happens because someone used SAM to size a territory instead of SOM.

The misconception

The most common mistake, especially in decks, is using SAM and SOM interchangeably. Founders and sales leaders will say "our addressable market is $2B" and then quietly mean SOM when they talk about this year's target. That's how you end up with a board deck that implies you're capturing 40% of a market you're actually capturing 2% of. SAM tells you the size of the pool. SOM tells you how many fish you can actually catch with the boat you have right now.

How it's really measured

SOM is usually built bottom-up from things you can actually count: current win rate, average sales cycle length, rep capacity, and realistic market share against named competitors, not top-down as a percentage guess of SAM. A SOM number that isn't grounded in your actual close rate and rep capacity is just a hopeful fraction of SAM with better formatting.