How to Describe Your Market Size on the YC Application

This page covers exactly how to calculate and write your market size, the difference between TAM, SAM, and SOM as YC actually uses them, and the specific mistakes that make this field weaker rather than stronger.

The market size field is testing three things simultaneously, and most founders only address the first:

1. Is the market large enough to justify a venture-scale outcome?

This is the obvious question and the one most founders address. But size alone is not the full test.

2. Do you understand your market specifically enough to have calculated this number yourself?

A bottom-up calculation — starting from your specific user, your specific pricing, and a real count of how many such users exist — demonstrates market understanding. A top-down citation of a Gartner or Statista figure demonstrates that you can use a search engine, which is a much weaker signal.

3. Is your market size argument connected to your actual product, or is it generic to the category?

"The global healthcare market is $8 trillion" is true and tells partners nothing about whether your specific glucose monitoring product for tier 2 Indian diabetics has a path to meaningful revenue. The market size argument needs to be scoped to what your product actually addresses.

Calculate your market size in three steps, each one narrowing from the last:

Step 1 — Total Addressable Market (TAM): the full population with this problem

Count the total number of people or businesses who have the problem you solve, multiplied by what they would realistically pay annually.

"India has approximately 8 lakh independent pharmacies. At our current pricing of ₹2,500/month (₹30,000/year), the TAM for pharmacy inventory software in India is ₹2,400 crore (~$288M) annually."

Step 2 — Serviceable Addressable Market (SAM): the portion you can realistically reach with your current model

Narrow to the segment your specific distribution and product can actually serve, given known constraints (geography, language, business size, regulatory scope).

"Of those 8 lakh pharmacies, approximately 5 lakh are in the tier 2 and tier 3 cities where our WhatsApp-native, no-training-required approach has the strongest fit — versus tier 1 cities where competitors with desktop software already have stronger penetration. Our SAM is therefore approximately ₹1,500 crore (~$180M) annually."

Step 3 — Serviceable Obtainable Market (SOM): what you can realistically capture in a defined timeframe

State a specific, defensible percentage of the SAM you could capture in 3-5 years, grounded in your current growth rate and distribution capacity, not an arbitrary aspirational number.

"At a realistic 5% market penetration of our SAM within 5 years — consistent with the penetration rates achieved by comparable vertical SaaS products in adjacent Indian markets — our SOM is approximately ₹75 crore (~$9M) in annual recurring revenue."

For population/business counts:

Use government data, industry association reports, or census data rather than marketing reports from software vendors. For India specifically: Ministry of MSME data, RBI reports for financial population data, NSSO surveys for informal economy sizing, and state-specific trade association data for vertical-specific counts (such as pharmacy associations, retailer associations).

For pricing assumptions:

Use your own validated pricing, not an assumed "what the market could bear" figure. If you have not yet validated pricing with real customers, state the pricing you are testing and note that it is provisional: "We are currently testing ₹2,500/month and will refine this TAM calculation as pricing validates further."

For penetration rate benchmarks:

Cite comparable companies' actual achieved penetration rates if you can find them (public filings, press coverage of growth metrics), rather than an arbitrary round number like "we'll capture 10% of the market." If no clean comparable exists, be explicit that your SOM estimate is a reasoned projection based on your current growth trajectory rather than an externally validated benchmark.

Showing your math:

Always show the calculation, not just the final number. "8 lakh pharmacies × ₹30,000/year = ₹2,400 crore" is more credible than "TAM: ₹2,400 crore" because it lets a partner verify your logic and catch any errors themselves, which builds trust rather than requiring blind acceptance of your figure.

Failure 1: Citing global TAM for a geographically or demographically specific product

If you are building for independent pharmacies in tier 2 India, citing "the global pharmacy software market is $4.2 billion" is irrelevant — your product does not address pharmacies in Germany or Brazil. Scope your TAM to what your product, your distribution, and your regulatory position can actually reach.

Failure 2: Using a single combined multiplier that obscures the calculation

"There are 1.4 billion people in India and even capturing 1% of them would be huge" is a famous and consistently rejected pattern — it does not specify who those people are, why they would pay, or how you would reach them. Every step of your calculation should be specific and defensible on its own.

Failure 3: Confusing market size with revenue potential without considering take rate or attach rate

For marketplaces and platforms, TAM should reflect the revenue you actually capture (GMV × take rate), not the full transaction value flowing through your platform. A ₹500 crore GMV marketplace with a 5% take rate has a revenue TAM of ₹25 crore, not ₹500 crore — state both figures clearly and do not let the larger GMV number stand in for your actual addressable revenue.

Failure 4: An unrealistic SOM that ignores your current growth rate

If your current growth rate would take 40 years to reach your stated SOM, the SOM figure is not credible. Ground your SOM specifically in your current trajectory extended at a reasonable, slightly accelerating pace — not an aspirational leap that has no connection to your actual current metrics.

Failure 5: Treating market size as a one-time calculation rather than connecting it to your actual go-to-market

The strongest market size answers connect directly to the distribution section of your application. If your SAM is defined as "tier 2 and tier 3 cities where WhatsApp distribution works best," your distribution strategy section should describe exactly how you reach that specific population, creating a coherent narrative rather than two disconnected sections.

"India has approximately 8 lakh independent pharmacies (Ministry of MSME estimate). At our validated pricing of ₹2,500/month, the TAM is ₹2,400 crore annually (~$288M). Our SAM is the approximately 5 lakh pharmacies in tier 2 and tier 3 cities, where our WhatsApp-native approach has the strongest product fit relative to desktop-based competitors who have already captured tier 1 markets — this gives a SAM of approximately ₹1,500 crore (~$180M). At our current growth rate of 22% MoM, sustained with continued expansion across the 340 pharmacy WhatsApp groups we have identified in Maharashtra alone, we project a realistic SOM of ₹75 crore (~$9M) ARR within 5 years, representing roughly 5% penetration of our SAM — consistent with penetration rates achieved by comparable vertical SaaS products in adjacent Indian markets like accounting software for SMBs."

This answer shows the calculation at every step, scopes the market to what the product actually addresses, and connects the SOM to the company's actual current trajectory rather than an arbitrary aspirational figure.