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.

Ryan's Take

Rule of 40 is one of those metrics that's useful at the right stage and misleading at the wrong one. Growth-stage SaaS: useful. Early-stage burning to grow: don't worry about it yet. Late-stage approaching profitability: critical. The discipline: know when the metric matters for your company, use it for capital allocation decisions (grow more vs become more efficient), and avoid optimizing for the metric at the expense of strategic decisions that compound long-term.

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.