What is the Rule of 40?
SaaS founders and investors argue endlessly about growth versus profit. The Rule of 40 settles it into a single, useful benchmark: together, they should add up to at least 40%.
Skip the math — the free rule of 40 calculator runs this from your own figures.
Open the free calculator →The rule in one line
The Rule of 40 says that a healthy software or subscription business should have a revenue growth rate plus a profit margin that together total at least 40%. Growing 30% with a 15% margin gives a score of 45 — a pass.
It's popular because it captures a real trade-off in a single number: you can be a healthy business by growing fast, by being profitable, or by balancing the two — but not by being weak at both.
Why it balances growth and profit
Early-stage software companies often grow fast while losing money; mature ones grow slowly but profitably. The Rule of 40 lets both look healthy, as long as the combination is strong. A company growing 60% can 'spend' up to 20 points of negative margin and still pass.
That flexibility is the point. It doesn't demand profitability from a fast grower or fast growth from a profitable business — it demands that the sum be respectable.
Which numbers to use
Growth is usually year-over-year revenue growth as a percentage. Margin is a profit margin — commonly an operating margin or a free-cash-flow margin, though EBITDA margin is also used. The important thing is to be consistent about which margin you use so the score is comparable over time.
Because the choice of margin changes the score, always note which one you're using when you quote a Rule of 40 number.
What it doesn't tell you
The Rule of 40 is a quick health check, not a full diagnosis. It ignores absolute size, retention, unit economics, and the quality of growth. A company can hit 40 with unsustainable growth or one-off margin, so it should be read alongside metrics like net revenue retention and CAC payback.
Treat it as a fast filter: passing is a good sign, failing is a flag to investigate — but neither is the whole story.
Use it to steer trade-offs
The rule is most useful for decisions. If you're tempted to spend heavily to accelerate growth, the Rule of 40 shows how much margin you can give up before the combination weakens. If growth is slowing, it shows how much margin you need to compensate.
The free calculator below scores your growth and margin against 40 instantly, and the full tracker charts it quarter by quarter so you can see the trend.
Questions
Does the Rule of 40 apply to early-stage startups?
It's most meaningful once a company has enough revenue and history for growth and margin to be stable and comparable — typically at scale-up stage rather than the earliest days. Very early startups often have erratic growth and deeply negative margins as they invest, so the score swings wildly and means less. As a business matures past the initial ramp, the Rule of 40 becomes a more reliable health check.
Is a score above 40 always good?
Usually a positive sign, but not a guarantee. A high score built on unsustainable growth, a one-time margin boost, or under-investment in the future can flatter the number. That's why the Rule of 40 should be read alongside the quality of growth (retention, unit economics) rather than in isolation. Passing is encouraging; it just isn't the entire picture.