Rule of 40 (growth rate + EBITDA margin ≥ 40) has become the canonical SaaS health metric. It's useful as a benchmark and incomplete as a management tool. Understanding what it's actually measuring — and what it's missing — makes you a better operator.
What Rule of 40 captures: the fundamental growth-profitability trade-off in SaaS. Growing fast requires investing in sales, marketing, and engineering. Investing compresses margins. Slowing down improves margins but reduces future revenue potential. Rule of 40 says you can make either choice as long as the sum is 40.
What Rule of 40 doesn't capture:
Revenue quality. A company growing 50% with -10% EBITDA scores 40, whether that 50% growth comes from high-retention enterprise customers or churny SMB accounts with 70% GRR. The composition of growth matters for the quality of the underlying 40.
Cash efficiency. EBITDA isn't cash. A company with 0% EBITDA margin could have positive or negative free cash flow depending on working capital dynamics, capitalized development costs, and capital expenditures. Two companies with the same Rule of 40 score could have very different cash positions.
The path to 40. There's a meaningful difference between a 20-20 Rule of 40 (moderate growth, moderate margins) and a 60-(-20) Rule of 40 (high growth, high burn). The first is a sustainable business that can self-fund. The second requires continuous capital access to sustain itself.
The relevant benchmark in 2026 is not just "are you above 40" but "how are you above 40?" Sustainable above-40 companies are growing on efficient CAC, investing in retention, and expanding margins as they scale. Unsustainable above-40 companies are buying growth with unprofitable CAC and hoping to figure out margins later.
Shoot for 40. But care about the composition.