Rule of 40

The Rule of 40 is the SaaS heuristic stating that revenue growth rate plus profit margin should be 40% or more. The metric provides a single number balancing growth (which drives valuation but costs cash) and profitability (which signals capital efficiency). It is widely used by SaaS investors as a quick health check at growth and scale-up companies, with the underlying logic being that companies should either grow fast enough to justify burn (high growth + negative profit OK) or be profitable enough to justify slower growth (modest growth + positive profit OK). It is a useful directional metric and one frequently misapplied at early-stage where the math doesn't work yet.

The calculation:

Basic formula:

• Rule of 40 = Revenue Growth Rate (%) + EBITDA Margin (%)
• Should equal 40% or more for a "healthy" SaaS company.

Examples:

• 50% growth + (-10%) EBITDA margin = 40 (passes).
• 30% growth + 10% EBITDA margin = 40 (passes).
• 20% growth + 25% EBITDA margin = 45 (passes).
• 100% growth + (-30%) margin = 70 (strongly passes).
• 20% growth + (-25%) margin = -5 (fails badly).

Where Rule of 40 applies well:

Growth-stage SaaS ($50M-$500M ARR): the metric is most-meaningful in this range. Mature enough that profitability matters; still growing fast enough for the metric to capture both.

Public SaaS comparisons: investors use Rule of 40 to compare across SaaS companies. Top performers exceed 40.

Capital allocation decisions: deciding whether to grow more aggressively (potentially reducing margin) or invest in efficiency (potentially reducing growth) often references the metric.

Where Rule of 40 applies poorly:

Early-stage (< $20M ARR): companies typically have high growth and very negative margins. Math doesn't translate to "healthy" the same way.

Non-SaaS businesses: the heuristic was developed for SaaS; doesn't translate directly to other models.

One-time inflection points: companies undergoing major changes (large investments, M&A, market shifts) may temporarily fall below 40 without indicating long-term health issues.

Adjusted variants:

• Some investors use Rule of 50, Rule of 60 for higher-growth companies (more aggressive standard).
• Free cash flow margin sometimes substituted for EBITDA margin.

What founders get wrong: Either obsessing over Rule of 40 at early stage where it doesn't apply meaningfully, or ignoring it past growth stage where it does. The right discipline: use the metric at growth-stage when it matters, in capital allocation contexts, while remembering it's a heuristic not a target.

Related: Magic Number · EBITDA · Growth Strategy · Financial Projections · Unit Economics

FAQ

What is the Rule of 40?
A SaaS heuristic stating that a healthy company should have combined revenue growth rate and profit margin (typically EBITDA margin) of 40% or more. Provides a single metric balancing growth (which drives valuation but costs cash) and profitability (which signals capital efficiency).

How is Rule of 40 calculated?
Revenue Growth Rate (%) + EBITDA Margin (%). Example: 30% growth + 10% margin = 40 (passes). Or 50% growth + (-10%) margin = 40 (also passes; high growth justifies modest negative margin).

When does Rule of 40 apply?
Most meaningful at growth-stage SaaS ($50M-$500M ARR), public SaaS comparisons, and capital allocation decisions. Less applicable at early-stage (where growth is high and margins very negative) and non-SaaS businesses.