What is the Rule of 40?
The Rule of 40 is a SaaS heuristic stating that a healthy SaaS company’s combined growth rate and profit margin should be at least 40%. The formula is intentionally additive: growth and profit are treated as substitutable: a company can be high-growth/low-profit (e.g., 60% growth + -20% margin = 40) or low-growth/high-profit (e.g., 10% growth + 30% margin = 40), and both pass the test. The Rule of 40 became the dominant SaaS valuation benchmark from 2015 onward, especially during the 2020-2023 efficiency-focused investor pivot.
Rule of 40 formula
Rule of 40 = Revenue Growth Rate (%) + Free Cash Flow Margin (%)
- Revenue growth: YoY ARR growth or LTM revenue growth.
- Profit margin: commonly Free Cash Flow margin; some variants use EBITDA margin or operating margin.
- Threshold: 40% is benchmark; 60%+ exceptional; 30%+ acceptable for early-stage.
Rule of 40 interpretation
- Growth-heavy SaaS: 80% growth at -40% margin → Rule of 40 = 40 (passes). Common at Series B-D.
- Balanced SaaS: 30% growth at 10% margin → Rule of 40 = 40 (passes). Public SaaS norm.
- Profitable SaaS: 10% growth at 30% margin → Rule of 40 = 40 (passes). Mature SaaS.
- Below 40: investor concern: either growth or profit must improve.
Rule of 40 evolution and limitations
- 2015-2021 boom era: growth was rewarded over profit; Rule of 40 was permissive.
- 2022+ rationalisation era: profit margin component became more heavily weighted; “Rule of 40 with positive FCF” is the new bar.
- Sector variation: infrastructure and developer tools tolerate higher growth/lower margin; vertical SaaS expected to be more efficient.
- Macroeconomic sensitivity: capital cost (Fed funds rate) heavily affects acceptable margin-vs-growth trade-off.
Applying the Rule of 40 in Turkey
Turkish SaaS companies have adopted the Rule of 40 in line with US and EU practice, but nominal revenue growth driven by Turkish lira inflation should not be confused with real growth. A USD-based or inflation-adjusted Rule of 40 is a more honest signal. For SaaS companies serving the Turkish domestic market (especially SME-focused ones), margin pressure from macroeconomic conditions often makes the Rule of 40 hard to meet; scale and geographic diversification soften this effect.
Practical Guidance
- Calculate the Rule of 40 with FCF margin rather than EBITDA.
- In high-inflation contexts, also calculate an inflation-adjusted version.
- Compare the result with sector peers.