Rule of 40

A SaaS metric stating that a software company's combined growth rate and profit margin should exceed 40%.

The Rule of 40 is a popular financial rule of thumb used by growth investors, venture capitalists, and analysts to evaluate the performance and operational balance of software-as-a-service (SaaS) and other high-growth subscription businesses. It recognizes that assessing a company's health based on revenue growth or profitability in isolation can be misleading. A young software company may burn significant cash to fuel rapid expansion, while a mature firm may grow slowly but generate high cash flows. The Rule of 40 provides a single framework to determine if a company is scaling efficiently. To calculate the metric, investors add a company's year-over-year revenue growth rate to its profit margin. While GAAP operating margin or net margin can be used, analysts most commonly use Free Cash Flow (FCF) margin or EBITDA margin to capture the actual cash-generating power of the business. If the sum of the growth rate and the margin meets or exceeds 40%, the company is generally considered to have an elite, healthy financial profile. Investors care about this metric because it highlights the trade-offs of business expansion. A company with a score below 40% may be growing too slowly relative to the amount of cash it is burning, suggesting inefficient customer acquisition or a weak product-market fit. Conversely, a company exceeding 40% demonstrates that its growth is sustainable. A common pitfall for investors is relying on a single quarter's data, as seasonal fluctuations in cash flow or one-time revenue spikes can artificially distort the metric. It is best evaluated using trailing twelve-month (TTM) figures.

Company A is a cloud software provider that generated $100 million in revenue last year and $130 million this year, representing a revenue growth rate of 30%. During the same period, the company generated $13 million in free cash flow, which is a free cash flow margin of 13% ($13 million / $130 million). Adding these two percentages together yields 30% + 13% = 43%. Because 43% is greater than the 40% threshold, Company A successfully satisfies the Rule of 40.