Why does Rule of 40 matter?
It is the shorthand later-stage investors and public markets use to decide whether losses are buying growth at a defensible rate, which makes it the frame an early company will eventually be judged in. It is useful earlier as a way of thinking rather than a score: it says explicitly that cutting burn and growing faster are two routes to the same place, so a company that cannot accelerate is not out of options. It also explains why an unplanned slowdown hurts twice over: the growth term falls immediately, while the spending that was meant to produce that growth is already committed, so the margin term does not improve to compensate until the cost base is cut.
What does Rule of 40 look like in practice?
Suppose a company grows revenue 60% year over year at an operating margin of minus 25%. That sums to 35, just under the line. A second grows 20% with a positive 25% margin and sums to 45, comfortably over it, while growing a third as fast. At seed stage the arithmetic stops meaning anything: a company going from $200k to $800k of ARR is growing 300% on a margin of several hundred percent negative, and the sum is noise. The rule starts to bite around the point where growth rates fall into double digits and the margin term stops dominating.
What are the common mistakes with Rule of 40?
- Applying it before product-market fit, where both inputs are too small and too volatile to say anything.
- Leaving the definitions unstated. ARR growth and recognized revenue growth differ, as do EBITDA, operating margin, and free cash flow margin, and a quoted figure without its definitions is not comparable to anyone else's.
- Treating 40 as pass or fail rather than a trade curve. What a reader takes from it is the mix, not the total.
- Hitting the number by cutting the spending that produces next year's growth, which moves the problem one year out and makes it larger.
Related concepts
- ARR, MRR, and ACVThree ways of counting recurring revenue: annualized run rate (ARR), the monthly equivalent (MRR), and the average value of one contract (ACV).
- Gross MarginRevenue minus the direct cost of delivering the product, as a percentage of revenue, the share of each dollar left over to fund everything else.
- Burn MultipleNet burn divided by net new recurring revenue over the same period. The number of dollars the company consumes to add one dollar of recurring revenue.
- Default Alive vs. Default DeadA company is default alive if its current growth and spending trends reach profitability before the cash runs out without raising again; default dead if they do not.