How do you answer market sizing questions on interviews?

Market sizing is about speed and precision in balance—getting a quick, reliable number when needed or going deep when you are required to. But while market sizing helps you understand the opportunity at hand, what truly matters is understanding who buys from you and why.

For a startup, it’s often about quick sizing: TAM (Total Addressable Market) back-of-the-envelope calculations using industry benchmarks, competitor data, and first-principles thinking. You estimate the number of potential customers, their willingness to pay, and triangulate using multiple sources. Fast, directional, good enough to decide if a market is worth chasing.

For a mid-size or scaling company, you get more structured: layering in proprietary data, segmenting customers, and refining assumptions with surveys or sales insights. You move beyond just TAM and into SAM (Serviceable Addressable Market) and SOM (Serviceable Obtainable Market) to focus on what’s actually within reach.

For an enterprise, it’s full-scale research. Market dynamics, competitive landscapes, and economic trends shape multi-year strategy. This is where financial modeling meets qualitative insights—talking to customers, analyzing adoption curves, and stress-testing assumptions.

For across company sizes, you will want to partner with someone in data and/or rev ops to help you get the right data to do the analysis.

But the real unlock isn’t just how big the market is—it’s whether the right company profiles exist in enough volume to sustain growth.

- Who are they?
- What problem do they need solved?
- How do you serve them better than alternatives?
- Where do you sit within the competitive and ecosystem dynamic?
- And crucially—at what point does the market saturate for you?

Market sizing is a means to an end. The real goal is framing not just the opportunity but the path to capturing it, ensuring you don’t just play in a big market, but actually win in it. Importantly, you're presenting or some executive will leverage it in presentation for decision making, you want to make sure you're providing insights and not just data.