When you show a market-sizing slide, investors aren't checking your math. They're checking whether you've actually thought about the market beyond the slide. The two questions they ask are almost always the same:

1. "How did you get to that account count?"

If your slide says "30,000 potential customers," they want to know the source. Acceptable answers:

  • A public dataset. "Crunchbase shows 30K B2B SaaS companies in our segment with 50+ employees." Cite the dataset.
  • A trade-association directory. "AICPA lists 18K accounting firms with 10+ partners." Specific and verifiable.
  • A buildable bottom-up. "We pulled US Census data on businesses with $5M+ revenue in [vertical] — 30K firms." Walk through the filter logic.

Unacceptable answers:

  • "We estimated based on industry research." (Whose research?)
  • "There are roughly 30K out there." (Roughly is a tell.)
  • "Our addressable market is about 10% of the broader category." (Top-down by a different name.)

If you don't have a real source, the right move is honesty: "Our best estimate is 25–35K based on triangulating Crunchbase and customer interviews; we'd refine this with diligence access to specific datasets." Honest uncertainty beats fake precision.

2. "How did you get to that ACV?"

The contract value side is where most founders fudge. The right answer triangulates three reference points:

  • Your current customer average. "Today our blended ACV is $32K across 15 customers."
  • Your top-quartile ACV. "Our biggest customer is at $90K; the top quartile averages $65K."
  • Your projected maturity ACV. "We expect median ACV to land at $55K by year 2 as seats expand and we ship the enterprise tier."

Then defend the projection. "Maturity ACV from $32K to $55K assumes 1.7× seat expansion and 25% adopting the enterprise tier. We've already seen 1.4× seat expansion in our oldest cohort."

If you're pre-revenue, the answer changes:

  • Comparable category pricing. "Tools in adjacent categories charge $30–80K for similar workflows."
  • Customer willingness to pay research. "Our 8 design partners signed LOIs at $40K–$60K annual."
  • Procurement benchmarks. "Industry data shows comparable software contracts at $40K median."

What doesn't fly: an ACV pulled out of thin air. "We think we can charge $80K" without a single data point will get probed and you'll fold under the questioning.

What the questions are really testing

Both questions test the same underlying thing: have you done the work to understand your specific market, or are you generalizing from a TAM slide?

Investors who back outliers fund founders who know their market in unusual depth. The TAM slide is the litmus test for that. If your two answers are crisp, specific, and sourced, you've passed the test and the partner moves on to other questions. If you stumble, the rest of the meeting plays defense.

The 10-minute prep

Before your next pitch meeting, write down your answers to both questions. Verbatim. Practice saying them aloud. If you can deliver each answer in under 60 seconds with confidence and at least one citation, you're ready.

If you can't, your market slide isn't done. Spend two hours sharpening before you take another meeting.