How to check TAM, SAM and SOM claims in a startup deck

Every deck has a market slide with a big number on it. The question isn't how big the number is. Ask how the founder got there.

Market sizing is the second of the six checks in our guide to evaluating early-stage startups in India, and it's one you can run alone, before the first call. You don't need the data room. You need the slide, a spreadsheet and an hour.

Investors do weigh it. In a survey of venture capitalists by Paul Gompers, Will Gornall, Steven Kaplan and Ilya Strebulaev, 68% of firms named the market as an important factor when choosing investments. That sample was mostly American; India hasn't published its own. But you'll hear the same question in any Mumbai, Delhi or Bengaluru partner meeting. Is this market real?

What TAM, SAM and SOM mean for an investor

TAM, the total addressable market, is the yearly spend on the problem if every possible buyer paid. SAM, the serviceable market, is the part this product and geography can serve. SOM, the obtainable market, is what the company can realistically win in a few years with its current team and channels. For an early investor, SOM matters most.

Why? Your money funds the next three years. Not the next thirty. A TAM in the tens of thousands of crores doesn't help a company whose sales team can reach two cities.

Why top-down numbers mislead

A top-down market size starts with an industry figure and takes a slice of it. It's fast and it looks impressive, but it tells you how big the industry is, not how many buyers this company can reach. The slice is usually a guess dressed as a percentage.

Here's a familiar version. A startup selling compliance tools to other startups puts India's count of DPIIT-recognised startups on its slide: over 2.3 lakh, according to a Press Information Bureau backgrounder from June 2026. The number is accurate. As a market, it's not. How many of those companies are active? How many have revenue? How many would pay for a tool rather than ask their CA?

You won't find those answers on the slide. That's the point.

A market size is a claim about customers. Ask to meet some of them.

Rebuild the market bottom-up

A bottom-up market size multiplies three numbers you can check: the buyers the founder can name, the price those buyers pay, and the share the current team can reach. It's smaller than the top-down figure almost every time. It's also the only version you can test against the company's own pipeline and invoices.

Count buyers you can name

Not "SMEs in India". Which SMEs? In which cities? Ask for the list, or ask how the founder built it, whether from a trade association's member directory, Udyam registrations for one district, Google Maps listings for Pune, Hyderabad and Chennai, or the company master data at the Ministry of Corporate Affairs. If they can't show you the source, the count is a guess. Say so.

Check the price on real invoices

Founders price their market at list price. Customers pay something else. Ask for five recent invoices, with the GST lines visible, and use the average. Discounts, months given away and pilots at cost all shrink the number, and they're common in Indian B2B sales, where a first deal often comes in below list.

Ask what the team can reach

How many sales calls can the current team make in a quarter? What share close? Work it forward three years, keeping the team the size it is today plus whatever this round actually pays for, and you'll have a SOM you can defend in your own investment committee. It's often a tenth of the slide. Sometimes less.

Sample (illustrative numbers): a startup sells billing tools to dental clinics in six cities. It can name 12,000 clinics. Real invoices average ₹30,000 a year, so the Sample SAM is ₹36 crore. If the team can win 15% of those clinics in three years, the Sample SOM is 1,800 clinics, or ₹5.4 crore a year. That's a real business. It's not the headline figure on the slide.

Questions to ask the founder

Ask questions that make the founder walk you through the build, not defend the total. A founder who knows their market will answer from memory, with names and prices. A founder who borrowed the number from a report will reach for the report. Both answers tell you something about how they'll run the company.

• Where does your top-line number come from, and what year is it?
• How many buyers can you name today, and how did you build that list?
• What did your last five customers actually pay?
• How many of your named buyers can this team reach in three years?
• Which part of this market would you give up first if money ran short?

Then compare the answers with what you learned about the person. Our post on checking a founder's background covers that side. A founder with years inside the industry tends to size the market from customers they've met. One who's new to it sizes it from reports. Neither is wrong, but you'll weigh the slide differently.

What to do with the number

Write your own bottom-up SOM next to the founder's figure and keep both. The gap between them is the most useful thing on the page. It shapes your price, and it gives you a test you can rerun each quarter against the company's pipeline. If you go on to price the round, our note on early-stage valuation methods picks up from here.

At MyStartupValley, market sizing is one of six due diligence parameters our team evaluates each startup on, alongside founder verification, cap table, legal, client agreements and compliance. If you'd like companies that arrive with that work done and deal notes written by our team, see the investor workspace.

Questions

What is the difference between TAM, SAM and SOM?

TAM is the total yearly spend on the problem if every possible buyer paid. SAM is the part of that spend the company's product and geography can serve. SOM is the share it can realistically win in the next few years with the team and channels it has.

How do investors check a startup's market size?

They rebuild it bottom-up. Count the buyers the founder can name, multiply by a price confirmed on real invoices, then ask how many of those buyers the current sales team can reach in three years. If the founder's slide is far above that figure, ask where the gap comes from.

Is a large TAM a good sign for an early-stage startup?

Not by itself. A large TAM built from an industry report says little about this company. A smaller market built from named buyers and real prices is more useful, because you can test it and track it as the company grows.

Sources: Gompers, Gornall, Kaplan and Strebulaev, How Do Venture Capitalists Make Decisions?, NBER Working Paper 22587, 2016 (Journal of Financial Economics, 2020) · Press Information Bureau, Empowered Youth, Stronger Nation (backgrounder), 13 Jun 2026