Article · ~10 min read

Bottom-Up Market Sizing: What It Is and How to Do It

Angelina Graumann · Visible.vc Free Intermediate

This is written by Visible, a platform that sits on the investor side of the table, so it explains bottom-up sizing the way a VC actually reads it. It is direct about why the top-down number collapses under scrutiny and why the bottom-up build wins credibility, which is exactly the tension you are describing. Use it to decide what to lead with, then show top-down only as a sanity check.

• Bottom-up sizing (count real customers, multiply by realistic revenue per customer) is more defensible because every assumption is one an investor can poke at and you can answer.
• A top-down number pulled from an industry report signals you Googled a big figure rather than understanding who buys, how many exist, and what they pay.
• The strongest move is to lead with your bottoms-up number and use top-down as triangulation: if the two diverge a lot, revisit your assumptions before the meeting.