What’s the best way to size the TAM for a niche B2B software tool?

[Hannah27]

I’m trying to size the total addressable market for a niche B2B software tool, but I’m stuck on whether to use a top-down industry report figure or build a bottom-up model from my own lead list. The top-down number feels too broad and optimistic for realistic market share projections.

[Oliver32]

I tried both routes. The top down figure from an industry report looked big and easy, but it stretched reality for a tiny niche. My gut said the bottom up from actual leads had more teeth

[DavidRH]

I built a quick bottom up model using my current leads and a few conversion assumptions. It was messy but it matched the sales cycle and slice of the target segment I actually see

[Penelope.J]

We ran a sensitivity pass on pricing and funnel drop offs. Small tweaks in conversion rate moved TAM a lot more than we expected, which was both reassuring and scary

[Noah_H]

One thing I did not like about top down is you end with a percentage of a big market which you cannot really own. It feels out of reach

[JeffreyUG]

I kept a loose mix approach. I used a big market baseline then constrained it with a bottom up cap based on our ICP count and close rate

[JackC]

Maybe the real issue is how we define the ICP and the sales cycle rather than the market size itself?

[Sofia33]

I would not lock a single number that early and would keep two scenarios on the board for early stage planning and fundraising