What’s the best way to estimate tam for niche b2b software for architecture firms?

[JustinP]

I’m trying to map out the market for a new B2B software tool, but I keep hitting a wall when I try to estimate the total addressable market size for our specific niche. My initial numbers feel way off because I can’t find reliable data on how many small architectural firms actually use a project management system versus just spreadsheets. How do you all get comfortable with your TAM figure before presenting it to potential investors?

[Mila.T]

I’ve found that TAM is less about a precise number and more about a defensible range you can live with. I start with the number of architectural firms in the ICP region, then layer in a rough adoption rate for PM tools based on proxy data from construction software surveys and the size of typical projects. Then I apply a price per year and cap it with a reasonable churn and upsell assumption. The key was to show a few scenarios to investors rather than a single point.

[OliverH]

TAM is a trap, but you can still make it work by triangulating. I did bottom-up to sanity-check a top-down estimate. Count target firms, assume each firm would buy a basic PM package for a yearly fee, add a growth rate for larger firms, and then trim for expected penetration. Then I cross-check by looking at overall software spend in the industry and see if the numbers line up. The range felt ugly but credible, and we used it as the anchor for investor conversations.

[Paul_T]

One concrete action I took was a 90 day pilot with three small firms to see if PM tools actually improved project tracking. We tracked time-to-status updates, meeting cadence, and a simple value signal from the team. Adoption stayed at about a third of users, which dragged the ARR projection down, so we widened the TAM to cover broader capabilities.

[Anthony_P]

Do you think the problem here is really the TAM or that we don’t have good data on adoption rates?