Ideas & Opportunity

Investors keep asking for a top-down TAM slide, but I built my number bottoms-up. Which do I show?

A starting point

Show both, but let the bottoms-up number lead and treat the top-down as context. Bottoms-up (customers times price times frequency) proves you actually understand who buys and why, which is what a real investor is testing; the top-down number just frames the ambition. As a starting point, if you can only defend one, defend the bottoms-up one, because that's the one that survives a follow-up question.

Go deeper

Hand-picked from around the web, each with a note on why it earns your time.

3 resources 3 link-checked Watch Read Use

Watch

▶️ Video
✓ Link checked Free Intermediate

Why we picked it This is the investor's side of your exact question: Steve Barsh, a managing partner at Dreamit Ventures, walks through what he is actually looking for behind the TAM ask and the mistakes that make him distrust a slide. He is blunt that the credible path is bottoms-up (number of customers times price you can defend), which validates your instinct. Watch it to hear how the person on the other side of the table reads the number you are about to show.

What is Total Addressable Market (TAM), with Steve Barsh

On Slidebean by Steve Barsh (Dreamit Ventures) ~10 min

  • Investors read the TAM slide as a test of whether you understand your buyer, not as a hunt for the biggest possible figure.
  • The common tells that lose trust: confusing TAM with today's market or the size of the problem, and quoting a price you have not actually tested.
  • Show your work: confirm the customers exist where you claim, and that your price reflects what people already pay, before the number goes on a slide.
Open slidebean.com →

Read

📄 Article
✓ Link checked Free Intermediate

Why we picked it 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 Market Sizing: What It Is and How to Do It

From Visible.vc by Angelina Graumann ~10 min read

  • 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.
Open visible.vc →

Use

📋 Template
✓ Link checked Free Intermediate

Why we picked it A concrete, copyable Google Sheet (no paywall, no credit card) that builds your number bottoms-up from customer segments and price, then runs a sensitivity analysis on penetration. Since your instinct was already bottoms-up, this gives you a clean, defensible artifact to actually show instead of a slide with one round number. It also frames SAM and SOM off the same build, so the whole market slide stays internally consistent.

Total Addressable Market Template (free Google Sheet)

From Visible.vc by Mike Preuss ~15 min to fill in

  • Build TAM by segment (for example SMB, mid-market, enterprise), each with its own count and price, so the total is a sum of assumptions you can defend line by line.
  • The sensitivity table shows revenue across different penetration rates, which reframes the conversation from a single big number to a realistic range you can capture.
  • Copy the sheet to your own Drive and swap in your real numbers; it is a working model, not a static PowerPoint, so an investor can interrogate the inputs live.
Open visible.vc →

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