What is the rule of 40 in startups?

What Is the Rule of 40 and Why It Matters for Startups

When evaluating the health of a SaaS startup, investors and founders often turn to a simple but powerful benchmark: the Rule of 40. At its core, this rule states that a company’s revenue growth rate plus its EBITDA margin should equal at least 40%. For example, if a company is growing at 30% annually, it can afford an EBITDA margin of 10%. Or, if it’s not yet profitable, its growth rate should be high enough to compensate—say, 50% growth with a -10% margin.

The Rule of 40 strikes a balance between growth and profitability—two forces that often pull in opposite directions. In the early days, startups typically prioritize rapid expansion, accepting losses to capture market share. As they mature, the pressure to become financially sustainable increases. This metric helps stakeholders assess whether a company is on a sustainable path, especially when comparing performance across similar-stage businesses.

It’s not a rigid law, though. The rule works best as a guidepost rather than a mandate. Industries vary, market conditions shift, and companies with a massive total addressable market might justify exceeding the threshold in pursuit of long-term dominance. Still, falling significantly below 40% over time can signal inefficiencies or misaligned strategy.

Ultimately, the Rule of 40 is less about hitting a number and more about understanding trade-offs. Founders who grasp this balance are better equipped to make informed decisions—whether it’s tightening costs, doubling down on sales, or preparing for the next funding round. In the fast-moving world of startups, that clarity can make all the difference.