The Rule of 40 Explained: Balancing Growth and Profitability in SaaS
The Rule of 40 says a healthy SaaS company’s growth rate plus profit margin should exceed 40%. Here is how to calculate it, what counts as profit, and where it breaks down.
As capital got more expensive, "growth at all costs" gave way to a tidier benchmark: the Rule of 40. It is the single most quoted shorthand for SaaS health because it captures the core trade-off every software business makes — growth versus profitability — in one number.
The formula
Rule of 40 score = revenue growth rate (%) + profit margin (%). Both inputs need definition. For growth, most use year-over-year ARR or revenue growth — closely related to your MRR growth rate annualised. For profit, the common choices are EBITDA margin, free-cash-flow margin, or operating margin; pick one and stay consistent. The point is the sum, not the components in isolation.
Illustrative Rule of 40 scenarios. Both growth and margin are valid paths to 40.
| Profile | Growth | Margin | Score | Passes? |
|---|---|---|---|---|
| High-growth, burning | 60% | -15% | 45 | Yes |
| Balanced | 25% | 20% | 45 | Yes |
| Profitable, slow | 10% | 25% | 35 | No |
| Stalled | 8% | 5% | 13 | No |
Why it matters
The rule forces an honest conversation about trade-offs. Fast growth justifies burning cash; slowing growth has to be paid for with margin. Companies that fail the rule are usually doing the worst of both — growing slowly and still losing money. Studies of public SaaS companies consistently find that those above 40 trade at meaningfully higher revenue multiples than those below.
Where it breaks down
- It is most meaningful at scale (roughly $10M+ ARR). Very early companies routinely "fail" it while doing exactly the right thing — investing ahead of revenue.
- It says nothing about durability — a one-off margin spike or unsustainable growth burst can flatter the score.
- Garbage in, garbage out: a weak gross margin caps how profitable you can ever be, so check unit economics underneath the headline number.
- It ignores retention quality — two companies can both score 42 while one grows on expansion revenue and the other on leaky new-logo acquisition.
Sources
- The Rule of 40 for SaaS companies — Bessemer Venture Partners
- Rule of 40 and SaaS valuation multiples — McKinsey & Company
- SaaS growth and profitability benchmarks — Benchmarkit
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