The Rule of 40 is a performance metric stating that a SaaS or high-growth company's growth rate plus profit margin should equal at least 40%. It helps investors assess whether a company is balancing expansion with profitability. A company growing 30% annually with a 10% margin meets the rule; one growing 50% but losing 20% does not, signaling unsustainable unit economics.

Why is Rule of 40 important for investors?

The Rule of 40 is a performance metric stating that a SaaS or high-growth company's growth rate plus profit margin should equal at least 40%. It helps investors assess whether a company is balancing expansion with profitability. A company growing 30% annually with a 10% margin meets the rule; one growing 50% but losing 20% does not, signaling unsustainable unit economics.

What is Rule of 40? | Angel Investors Network Glossary

The Rule of 40 is an investor benchmark used to evaluate whether a high-growth company is executing a sustainable business model. The rule states that a company's annual revenue growth rate plus its profit margin should total at least 40%. For example, a company with 35% growth and 5% profit margin meets the threshold. It's a quick way to determine if management is making smart trade-offs between scaling and profitability.

How It Works

The formula is simple: Growth Rate (%) + Profit Margin (%) = 40 or higher. Growth rate is typically measured as year-over-year revenue growth. Profit margin can be calculated as net income divided by revenue, though some investors use EBITDA margin for earlier-stage companies. A company prioritizing growth might hit 50% revenue growth but operate at -10% margin (still scoring 40). A mature company might grow 5% annually but maintain a healthy 35% margin, also meeting the threshold.

Why It Matters for Investors

This metric forces a conversation about trade-offs. Early-stage startups often sacrifice profitability for market share—investors accept this. But the Rule of 40 creates a financial reality check: unlimited losses aren't sustainable. If a company isn't growing fast enough to justify negative margins, it's burning cash without a path to unit economics. Conversely, if growth stalls while margins remain weak, the business model is broken. For angel investors and VCs, this rule screens out companies with neither growth momentum nor operational efficiency. It also helps identify when companies should shift strategies—moving from pure growth mode to sustainable profitability.

Example

Consider two Series B SaaS companies you're evaluating. Company A grows revenue 45% year-over-year with a -5% margin (Rule of 40 score: 40). Company B grows 20% annually with a 15% margin (Rule of 40 score: 35). Company A is reinvesting all profits into growth, which is reasonable given market opportunity. Company B is underperforming—it's neither growing aggressively nor profitable. Unless Company B has a clear path to accelerate growth or improve margins, it may signal execution challenges.

Key Takeaways

The Rule of 40 combines growth and profitability into a single health metric—neither dimension alone tells the full story.
Companies scoring above 40 are generally well-positioned; those below may need strategic intervention or closer scrutiny from investors.
This rule applies primarily to SaaS and recurring revenue businesses; it's less relevant for hardware or capital-intensive ventures.
Use it as a screening tool alongside other metrics like CAC, LTV, and burn rate for a complete due diligence picture.