How is the Rule of 40 calculated and when does it apply?

Full Explanation

The Rule of 40 is a benchmark used primarily for evaluating SaaS companies, stating that the sum of revenue growth rate (year-over-year) and profit margin (typically EBITDA margin or free cash flow margin) should equal or exceed 40%. A company growing at 60% with a -15% margin scores 45% and passes. A company growing at 20% with a 15% margin scores 35% and falls short. The formula is: Rule of 40 Score = Revenue Growth Rate (%) + Profit Margin (%). There is no universal agreement on which profit metric to use — EBITDA margin, operating margin, and free cash flow margin are all common. The choice should be consistent when comparing companies. The Rule of 40 is most meaningful for SaaS companies that have reached meaningful scale (typically £10 million+ ARR). At earlier stages, high growth rates make the metric trivially easy to pass, and at very early stages, neither growth rate nor margin is stable enough to be informative. The rule's value lies in its recognition that growth and profitability exist on a spectrum — a company can legitimately choose to prioritise growth over profitability (or vice versa), and the Rule of 40 provides a framework for evaluating whether the chosen trade-off is healthy. Companies scoring above 40% consistently command premium valuation multiples. Research from various sources suggests that each additional point above 40% correlates with approximately 0.5-1.0x higher EV/Revenue multiple. The best-performing public SaaS companies often score 50-70%, combining strong growth with improving margins. For private companies seeking investment or preparing for exit, the Rule of 40 is a useful communication tool. It allows founders to tell a coherent story about their growth-profitability balance and benchmark themselves against public market expectations.

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