What is Rule of 40?

Why It Matters

Rule of 40 gives investors, boards, and founders a single number to sanity-check whether a growth strategy is defensible, without getting into an argument over whether growth or profitability matters more in isolation. A company burning cash to grow fast isn't automatically unhealthy under this framework, as long as the growth rate is high enough to offset the losses, and a slower-growing but profitable company isn't automatically the safer bet either. It's especially useful when comparing two very different-looking businesses, since a fast unprofitable one and a slower profitable one can land on the same score and be judged roughly equivalent by this measure. Falling meaningfully below 40 is often treated as a signal that a company needs to either accelerate growth or improve margins, since it suggests neither lever is being pulled hard enough to justify the current trade-off. It's a blunt instrument rather than a precise valuation tool, but its simplicity is exactly why it gets used so often in SaaS fundraising and board conversations.

Example

A company grows revenue 35% year over year while running a 10% profit margin. Its Rule of 40 score is 35 plus 10, which equals 45, above the 40% threshold. A different company growing only 15% but running a 30% profit margin also scores 45 and is considered equally healthy by this measure, even though the two businesses look very different day to day, which is exactly the point of the benchmark: it treats fast unprofitable growth and slower profitable growth as potentially equal outcomes.

Frequently Asked Questions

• What counts as profit margin in the Rule of 40 calculation?

  It's typically EBITDA margin or a similar operating profitability measure, though some companies use free cash flow margin instead, so it's worth checking which definition a specific report is using before comparing scores.

• Is a company below 40 automatically in trouble?

  Not automatically, especially for very early-stage companies still finding product-market fit, but a score meaningfully and persistently below 40 is generally treated as a signal worth investigating rather than ignoring.

• Can a company score well on Rule of 40 with negative profit margin?

  Yes, as long as revenue growth rate is high enough to offset the negative margin and still sum to 40 or more, which is common for early-stage, high-growth SaaS companies investing heavily in expansion.

• How often is Rule of 40 calculated?

  Most commonly annually or quarterly, using trailing twelve-month growth rate and margin figures to smooth out short-term fluctuations.

• How does a company improve its Rule of 40 score?

  Either accelerating revenue growth, improving profit margin, or some combination of both, since the score only cares about the sum, not which lever moved.