The Rule of 40: The One SaaS Health Metric Every Investor Checks
The Rule of 40 combines revenue growth and profit margin into a single score that tells you whether a SaaS business is healthy. Here's how to calculate it, interpret it, and improve it.
What Is the Rule of 40?
The Rule of 40 states that a healthy SaaS company's revenue growth rate plus its profitability margin should equal at least 40%. It's a single-number framework for evaluating whether a SaaS business has found the right balance between growth and efficiency. A company growing 60% YoY with a −20% EBITDA margin scores 40. A company growing 20% with 20% margin also scores 40. Use our Rule of 40 calculator to score your business instantly.
Which Profit Margin to Use
EBITDA margin is the most widely used in private markets. FCF margin is increasingly preferred as a more honest representation. Operating margin is less common but useful for comparing companies with different D&A. When presenting to investors, be transparent — using FCF margin rather than EBITDA signals you're not trying to inflate the metric.
How to Interpret Your Score
- Below 20: Requires compelling explanation. Typically a fundraising obstacle.
- 20–40: Acceptable at early stages or during deliberate efficiency investments.
- 40–60: Healthy. Where most well-run growth-stage SaaS companies operate.
- Above 60: Outstanding. Shopify, Snowflake, and Veeva have sustained scores here during peak growth.
The Rule of 40 Is a Constraint, Not a Target
A common mistake is treating it as a target to optimise toward. It's a minimum health threshold. Two paths to a score of 40: (A) 60% growth, −20% margin — building market share aggressively with strong unit economics; (B) 15% growth, 25% margin — profitable but potentially harvesting at the expense of competitive position. At early stages, Path A is typically more valuable. The market prices each differently.
Improving Your Score
Accelerating growth requires investment that temporarily compresses margin. The bet is justified when payback periods are short and NRR is high. Improving margin without sacrificing growth is the hardest but most valuable improvement — it comes from operating leverage: fixed costs spread over larger revenue, improved gross margins, and sales efficiency gains. Companies sustainably above 40 have found product-market fit with low churn, high NRR, and a repeatable go-to-market motion.