What is the Rule of 40?
The Rule of 40 is a widely used benchmark for evaluating the health of a SaaS business by combining revenue growth rate and profit margin into a single score. The rule states that a healthy SaaS company’s revenue growth rate plus its profit margin should equal at least 40. A company growing at 30% with a 15% EBITDA margin scores 45 — it passes. A company growing at 20% with a 15% margin scores 35 — it does not pass by this measure.
The Rule of 40 was popularized in 2015 by venture capitalists Brad Feld and Fred Wilson as a quick way to assess whether a SaaS company is balancing growth and profitability appropriately. Its appeal is simplicity: it acknowledges that fast-growing companies are expected to sacrifice margin for growth, and that profitable-but-stagnant companies are sacrificing the future for the present. The rule penalizes neither trade-off — it just requires that the two dimensions sum to a minimum threshold.
Why 40? The number is empirically derived from analysis of public SaaS companies and does not have a rigorous mathematical basis. But it has proven to be a useful dividing line between companies that are efficiently deploying capital and those that are not. Public market data consistently shows that SaaS companies with Rule of 40 scores above 40 command meaningfully higher revenue multiples than those below.
Relative to neighboring metrics, the Rule of 40 is a higher-level composite indicator. Where burn rate and runway tell you whether the company can survive, and LTV:CAC tells you whether the unit economics work, the Rule of 40 tells you whether the business is being managed with the right balance of ambition and discipline.
The formula
Rule of 40 Score = Revenue Growth Rate (%) + Profit Margin (%)- Revenue growth rate — typically year-over-year ARR or MRR growth, expressed as a percentage. For example, if ARR grew from $5M to $7M, that is 40% growth. Use the same period consistently — quarterly or annual — and compare like-for-like periods.
- Profit margin — the choice of margin definition affects the result significantly. Common choices include EBITDA margin, free cash flow margin, and operating income margin. EBITDA margin is the most widely used because it adds back non-cash charges (depreciation, amortization, stock-based compensation) that distort operational cash generation. Free cash flow margin is preferred by some investors because it reflects true cash generation after capital expenditures. Whatever you choose, use one consistent definition.
Note: There is no division in this formula. It is a pure sum of two percentages. A company with 40% growth and 0% margin scores 40. A company with 0% growth and 40% margin also scores 40. A company with 60% growth and -20% margin scores 40 as well. All three are equivalent by this metric, though their trajectories and capital needs are very different.
Worked example
Default inputs: Revenue growth rate = 20%, Profit margin = 15%.
20 + 15 = 35A score of 35 falls below the 40 threshold. The company is profitable but its growth rate is not high enough to compensate for a modest margin. What can move the needle? Options include:
- Increase growth rate: Invest in sales capacity or marketing to push growth from 20% to 30%. At 30% growth + 15% margin = 45. The company now passes. But this investment typically reduces margin in the short term.
- Improve margin: Cut operating expenses to push margin from 15% to 25%. At 20% + 25% = 45. But constraining spend may slow growth, moving the growth component in the wrong direction.
- Both, in balance: The most durable path is to improve unit economics (reduce CAC, improve gross margin) so that growth becomes more efficient, allowing the score to rise without a direct trade-off.
What changes if growth accelerates to 40%? Even with a -5% margin (the company is burning cash), the score is 40 + (-5) = 35. This illustrates that raw growth does not automatically pass the Rule of 40 if losses are too deep.
Benchmarks
Rule of 40 benchmarks by stage and context:
- Below 20: A company in this range is typically either growing slowly and unprofitably or has a fundamentally weak business model. Investor scrutiny is high.
- 20–40: Acceptable for early-stage companies still investing in product-market fit and go-to-market. Not yet passing the rule but on a path that investors can underwrite if the trajectory is improving.
- 40–60: The healthy operating range for growth-stage SaaS. Companies above 40 consistently command ARR multiples of 8–15x in public markets.
- 60+: Best-in-class. Companies scoring above 60 (e.g., growing 80% with -10% margin, or 40% with 25% margin) trade at premium multiples and are considered benchmark companies in the public SaaS universe.
For early-stage companies (under $5M ARR), a high growth rate is more important than margin, and investors often accept scores below 40 as long as growth is above 100% YoY. At scale (above $50M ARR), where growth naturally decelerates, margin becomes increasingly important to maintaining a healthy score.
How to interpret and improve it
The Rule of 40 is most useful as a trend metric, not a point-in-time snapshot. A company with a score of 35 that was 25 a year ago is on a positive trajectory. A company with a score of 45 that has fallen from 70 is declining and warrants scrutiny.
The most effective way to improve the score depends on where you are in the growth curve. Early- stage companies should prioritize growth and accept lower or negative margins — the rule is designed to accommodate this through the growth-profitability trade-off. Later-stage companies (Series C and beyond, especially post-IPO) should optimize toward a balance that reflects their cost of capital and competitive position.
Common mistakes: Using quarterly growth instead of annual growth without adjusting for seasonality can distort the score. Also, including stock-based compensation in the margin calculation is inconsistent with the most common industry practice; SBC is typically added back under EBITDA-based definitions.
When the metric misleads: A score above 40 does not mean the company is well-managed. A business growing at 60% with -20% margin might pass the rule, but if that growth is driven by unsustainable discounting or channel stuffing, the score will collapse when those tactics normalize. Always interrogate the quality of both the growth rate and the margin.
Frequently asked questions
What is the Rule of 40? The Rule of 40 says a healthy SaaS company’s revenue growth rate plus profit margin should be at least 40.
Which profit margin should I use? Operators commonly use an EBITDA or free-cash-flow margin; use one consistent definition.