So you’ve got a killer idea—maybe it’s an app, a product, or a service. You’re excited, inspired… and then you hit the question every investor, mentor, and startup book asks: “What’s your market size?”
Cue the imposter syndrome. You’re not a business major. You don’t have spreadsheets filled with macroeconomic data. You just want to know: Is this idea worth chasing?
Good news: you don’t need an MBA to estimate your market size. In fact, with a laptop and 15 minutes, you can get a decent ballpark number. Here’s how.
Step 1: Understand the Three Levels of Market Size
Before we start Googling numbers, it’s important to understand what we’re estimating. Market size is usually broken down into three levels:
- TAM (Total Addressable Market) – If every possible person who could use your product did, how big would that be?
- SAM (Serviceable Available Market) – Of those, how many can you realistically reach based on geography, language, platform, etc.?
- SOM (Serviceable Obtainable Market) – Now, how many are likely to use your solution, considering competition and your current resources?
Step 2: Define Your Ideal Customer
Skip the jargon. Just ask: Who is my product for?
Let’s say you’re building a meditation app for parents of toddlers. Your ideal user is:
- A parent
- With kids aged 0–5
- Owns a smartphone
- Open to wellness apps
Got it? Now let’s get numbers.
Step 3: Google Like a Pro
Search terms like these can save you hours:
- “Number of parents with toddlers in [country]”
- “Meditation app usage statistics”
- “Market size of wellness app industry”
Write down the big stats. Don’t worry about perfection. You’re getting a directional sense, not preparing a Harvard case study.
Example:
- 20 million parents with kids under 5 in the U.S.
- 60% use smartphones
- 30% of smartphone users install wellness apps
So: TAM = 20M
SAM = 60% of 20M = 12M
SOM = 30% of 12M = 3.6M potential users
Boom. That’s your rough estimate.
Step 4: Multiply by Money
Let’s say you charge $5/month. If 3.6M people could pay you, that’s:
$5 x 12 months x 3.6M = $216M/year
Is everyone going to pay? Of course not. But even if you capture 1% of that, you’re looking at over $2M a year in revenue.
Step 5: Gut Check Your Numbers
Here’s how you know you’re in the right zone:
- Does this number feel believable?
- Are your assumptions too generous or too conservative?
- Would someone else with no background understand how you got this?
If yes, you’re golden.
Bonus Tools (If You Want to Go Deeper)
If you want to go beyond napkin math, here are a few powerful tools to help:
- ZetaResolutions.com – Use the Market Size Estimator module to quickly calculate your TAM, SAM, and SOM using built-in assumptions and real-world data. It’s a fast, guided way to get solid numbers—even if you’re not a numbers person.
- Statista – Great for finding up-to-date industry stats and reports.
- Google Trends – Helps you understand search interest and trends around your product or industry.
- U.S. Census / National Statistics – Ideal for demographic-specific insights.
- Niche Blogs & Industry Reports – Search for “<your industry> market report” to find deep dives from analysts and insiders.
Final Thoughts
Estimating your market size isn’t about getting the “right” answer. It’s about thinking strategically and showing that you understand who you’re building for. Investors don’t expect perfection—but they do expect logic.
So next time someone asks about your market size, you won’t freeze. You’ll smile, pull out your back-of-the-napkin math, and show them why your idea is worth betting on.
Ready to build that next million dollar idea? Check out our article on “The Ultimate Checklist for Starting a New Business” for some inspiration.