Market Sizing: TAM, SAM, SOM Made Simple
Learn how to calculate market size for any product. Master TAM, SAM, and SOM with simple examples and step-by-step instructions.
Prerequisites
- • Basic math skills
- • Understanding of your target customer
Market sizing helps you decide whether an opportunity is large enough to pursue.
Why market sizing matters
You're building a new feature. Your boss asks: "How big is the opportunity?"
Without market sizing, it is harder to compare opportunities, set goals, or see whether an idea is worth pursuing.
Market sizing helps product teams compare opportunities, plan resources, and explain their assumptions.
TAM, SAM, and SOM
TAM is the entire market under your chosen definition. SAM is the portion you could serve given product, geography, and segment. SOM is the portion you estimate you can win within a stated time horizon.
TAM (Total Addressable Market)
What it is: The total revenue if everyone in your defined market bought the product.
Simple formula:
TAM = Total Potential Customers × Average Price
Illustrative example: A meditation app
- Assume 250 million English-speaking smartphone users
- × $10/month subscription
- = $30 billion annual TAM
SAM (Serviceable Addressable Market)
What it is: The portion of TAM you can serve with your product, geographic reach, and business model.
What limits SAM:
- Geographic reach (which countries you operate in)
- Language (which languages your product supports)
- Platform (iOS only? Web only?)
- Customer type (only enterprises? only consumers?)
Illustrative example: Same meditation app
- Assume 50 million iOS users in the US, UK, and Canada
- × $10/month subscription
- = $6 billion annual SAM
SOM (Serviceable Obtainable Market)
What it is: The portion of SAM you estimate you can capture in the next 3-5 years, given your assumptions and the alternatives customers can choose.
What determines SOM:
- Your marketing budget
- Sales team size
- Current competition
- Product differentiation
Illustrative example: Same meditation app
- Assume 2% market share in five years: 1 million users
- × $10/month subscription
- = $120 million annual SOM
Start simple
Quick Start Exercise
Pick a simple product (coffee shop, gym, app) and answer:
- Who would buy this? (be specific)
- How many of these people exist?
- What would they pay?
- How many could you realistically reach?
- What percentage would choose you?
The bottom-up method
A bottom-up estimate starts with a defined customer group and makes its assumptions visible.
Step 1: Define Your Exact Customer
Too vague: "Small businesses." Better: "Independent restaurants with 10-50 employees in urban areas."
Step 2: Count Them
Find real data sources:
- Government databases (Census, Labor Statistics)
- Industry associations
- LinkedIn (for B2B)
- App store data (for consumer apps)
Step 3: Calculate Average Revenue
What will one customer pay you per year?
- One-time purchase: Price × purchases per year
- Subscription: Monthly price × 12
- Transaction-based: Average transactions × fee
Step 4: Apply Reality Filters
Not everyone will buy. Apply these filters:
- Awareness: What percentage will know you exist?
- Interest: Of those aware, who has the problem you solve?
- Ability: Of those interested, who can afford it?
- Action: Of those able, who will actually buy?
Illustrative examples
Example 1: Local fitness app
Product: Fitness app for busy parents
TAM Calculation:
- US parents with kids under 18: 63 million
- × $15/month subscription × 12 months
- = $11.3 billion TAM
SAM Calculation:
- Smartphone-using parents who exercise: 20 million
- × $180/year
- = $3.6 billion SAM
SOM Calculation:
- 0.5% market share (100,000 users) in 3 years
- × $180/year
- = $18 million SOM
Example 2: B2B Project Tool
Product: Simple project tracker for design agencies
TAM Calculation:
- Design agencies worldwide: 400,000
- × $2,000/year
- = $800 million TAM
SAM Calculation:
- English-speaking agencies with 5-20 people: 30,000
- × $2,000/year
- = $60 million SAM
SOM Calculation:
- Win 300 customers (1%) in first 3 years
- × $2,000/year
- = $600,000 SOM
Try It Now
Calculate your own market size:
Common mistakes
Mistake 1: Starting with a market-share percentage
"The market is $100 billion. We just need 1%!"
Why it can mislead: A percentage does not show how you will reach and win actual customers.
Better approach: Count actual customers you can reach and win.
Mistake 2: Using Old Data
Old data can make an estimate less useful, especially in a market that has changed.
Fix: Use the most current relevant data you can find, and record the source date and collection date.
Mistake 3: Forgetting Competition
Assuming you're the only solution ignores reality.
Fix: Research existing alternatives (including "do nothing") and estimate realistic share.
Mistake 4: Mixing Currencies
Adding USD, EUR, and GBP without converting.
Fix: Convert everything to one currency (usually USD) using current rates.
Quick Reference Checklist
Use this checklist for any market sizing exercise:
Define Your Market
- Specific customer description
- Clear problem you're solving
- Geographic boundaries
- Time period (annual, monthly)
Calculate TAM
- Find total customer count
- Determine average price
- Multiply and sanity check
Calculate SAM
- Apply geographic limits
- Apply platform/language limits
- Apply customer segment limits
- Recalculate with constraints
Calculate SOM
- Research competition
- Estimate realistic market share
- Consider your resources
- Apply timeline (3-5 years)
Validate
- Compare to similar companies
- Check against industry reports
- Get feedback from sales/marketing
- Test with customer interviews
Practical Applications for PMs
Feature Prioritization
Before building that enterprise feature:
- Count potential enterprise customers
- Estimate what they'd pay for it
- Compare to effort required
- Make data-driven decision
Setting OKRs
Use SOM to set realistic goals:
- Year 1: Capture 0.1% of SAM
- Year 2: Grow to 0.5% of SAM
- Year 3: Reach 1-2% of SAM
Resource Allocation
Market size justifies investment:
- $10M SOM = Small team, lean approach
- $100M SOM = Larger team, marketing budget
- $1B SOM = Major investment, multiple teams
AI Prompts for Market Sizing
Use these with ChatGPT or Claude to calculate your market size. For advanced analysis, check our PM Prompt Library.
Quick TAM/SAM/SOM Calculation
Calculate market size for [your product]: - What it does: [describe main value] - Target customer: [who buys it] - Price point: $[amount] per [month/year] Give me: 1. TAM with calculation steps 2. SAM with realistic filters 3. SOM for years 1, 3, and 5 4. Key assumptions to validate
Pro Tip: Use our full TAM/SAM/SOM Calculator prompt to walk through each layer with sanity checks.
Validate Your Numbers
Check if my market sizing is realistic: - My TAM: $[amount] - My SAM: $[amount] - My target SOM: $[amount] in [X] years Validate by: 1. Comparing to similar companies 2. Checking my assumptions 3. Flagging any concerns
Pro Tip: Our Market Opportunity Validator prompt checks assumptions and flags weak spots.
Size a New Feature
Should I build [feature name]? - Current product: [description] - Feature adds: [capability] - Development time: [weeks/months] Calculate: 1. Additional TAM this opens 2. Expected adoption rate 3. Revenue potential 4. ROI calculation
Pro Tip: Use our Feature Market Sizing prompt for detailed feature business cases.
Planning heuristics
Market Share: Rough Planning Heuristics
These are planning heuristics, not industry data. Treat them as a sanity check on your own bottom-up numbers, and expect wide variation by stage, segment, and category.
| Year | Illustrative share of SAM | Ambitious share |
|---|---|---|
| 1 | 0.1% - 0.3% | 0.5% |
| 3 | 0.5% - 2% | 5% |
| 5 | 2% - 5% | 10% |
Questions to test:
- What supports a plan to capture more than 10% of the defined market?
- TAM that includes unrelated customers
- SOM larger than successful competitors
- No clear path from current state to SOM
Key Takeaways
- Start with customers you can name and count
- Build from small (SOM) to large (TAM), not vice versa
- Use assumptions you can explain
- Use multiple methods to validate
- Update estimates as you learn more
Next steps
- Use our Market Sizing Calculator for guided calculations
- Learn Pricing Strategy to set the right price
- Understand CAC to know acquisition costs
Revisit the estimate as you learn more about customers, pricing, and competition.
Sources and Further Reading
- US Census Bureau - Population and business data
- Bureau of Labor Statistics - Industry employment data
- Statista - Market research and statistics
- Industry associations - Specific market data
- LinkedIn Sales Navigator - B2B company counts
- App Annie / Sensor Tower - Mobile app market data