Bottom-up is 2x more credible to investors. Lead with SOM (5-10% of SAM) not inflated TAM. 60% of pitch decks feature inflated market sizes—investors penalize '1% of $10B' logic.
Bottom-up market sizing is 2x more credible to investors than top-down in 2026. Investors now prioritize SOM (Serviceable Obtainable Market) over TAM because it reflects execution capacity. 60% of pitch decks feature inflated TAM figures—investors increasingly penalize '1% of a $10B market' logic. Top-down: starts with industry reports and narrows down. Bottom-up: builds from unit economics (customers × ARPU). Emerging: Value-Theory Approach for disruptive products where historical data doesn't exist.
Key Market Sizing Methods Takeaways
- Bottom-up is 2x more credible—shows customer understanding
- 60% of pitch decks have inflated TAM (investors penalize this)
- SOM is the new focus: 5-10% of SAM, achievable in 3-5 years
- TAM threshold: $1B+ for VC, $100M-$500M for angels/bootstrap
- Value-Theory Approach: emerging best practice for AI/disruptive products
- Use both methods for cross-validation, lead with bottom-up
Market sizing methods Facts
2x
more credible (bottom-up)
F22 Labs 2026
60%
of decks have inflated TAM
Pitch Deck Analysis 2025
5-10%
typical SOM as % of SAM
Startup Benchmarks
$1B+
TAM threshold for VCs
VC Industry Standard