Understanding Rule of 40 – and Why It Matters

The Rule of 40 is the single most useful constraint for separating sustainable growth from hype. It's simple, it's honest, and it forces you to ask the right question: is this company growing fast enough to justify burning cash?

What Is the Rule of 40?

The Rule of 40 says that a healthy growth company's revenue growth rate plus its profit margin should exceed 40%. That's it. One number. One threshold.

THE RULE OF 40 FORMULA

Revenue Growth (%) + EBITDA Margin (%) ≥ 40

A healthy growth company's combined score must meet or exceed 40 to be sustainable.

RULE OF 40 EXAMPLES

Company A – PASSES

Revenue Growth: 60%

EBITDA Margin: −15%

Rule of 40: 45

Growing fast enough to offset losses

Company B – FAILS

Revenue Growth: 20%

EBITDA Margin: −5%

Rule of 40: 15

Not growing or profitable enough

The concept comes from venture capital, where investors needed a quick way to assess whether a high-growth company was on a sustainable trajectory. It's since been adopted widely across public market growth investing.

KEY PRINCIPLE: CONSTRAINT ON ENTHUSIASM

GrowthPicks uses Rule of 40 as a constraint on enthusiasm, not a scoring input. A high Rule of 40 doesn't automatically make a stock attractive. But a low Rule of 40 forces a harder question: if this company isn't growing fast enough to offset its losses, why are we paying a premium for it?

Why GrowthPicks Uses It

In the GrowthPicks framework, Rule of 40 acts as a reality check. It doesn't replace judgement – it structures it. A company can score well on growth and quality but still deserve caution if its Rule of 40 is deteriorating.

How to Calculate It

You need two numbers:

TTM Revenue Growth (%) – trailing twelve months, year-over-year
EBITDA Margin (%) – EBITDA divided by TTM revenue

Add them together. That's your Rule of 40 score.

CALCULATION EXAMPLES

Company A – HEALTHY

TTM Revenue Growth: 35%

EBITDA Margin: 12%

Rule of 40: 47

Growing at healthy clip with positive margins

Company B – CAUTION

TTM Revenue Growth: 25%

EBITDA Margin: −5%

Rule of 40: 20

Decelerating growth, still losing money

What "Good" Looks Like

RULE OF 40 SCALE

50+

EXCELLENT

Strong growth with positive or near-positive margins

40–50

HEALTHY

On track. Balance between growth and profitability

30–40

CAUTION

Growth slowing or margins thin. Needs improvement path

Below 30

CONCERN

Warning sign unless very specific, time-limited reason

Common Mistakes

Using adjusted EBITDA instead of GAAP EBITDA. Companies love to add back stock-based compensation, restructuring charges, and anything else that makes the number look better. GrowthPicks uses GAAP numbers. Adjusted stories don't override economic reality.

Ignoring the direction. A Rule of 40 score of 42 is fine – unless it was 55 two quarters ago. The trend matters as much as the absolute number. A deteriorating Rule of 40 is a signal that something in the growth story is changing.

Treating it as a score. Rule of 40 is a constraint, not a ranking. Two companies with identical Rule of 40 scores can have completely different risk profiles, competitive positions, and investment cases. The number tells you whether enthusiasm is justified. It doesn't tell you how much to invest.

How It Appears in GrowthPicks

On every Detail page, you'll find the Rule of 40 displayed in the financials section. On the Compare page, you can sort the universe by Rule of 40 to quickly identify which companies are above and below the threshold.

In the scoring model, Rule of 40 contributes to the overall conviction signal, but it's explicitly designed to cap enthusiasm rather than generate it. A company with explosive growth but a collapsing Rule of 40 will see its Value Signal restrained – even if the growth numbers alone look attractive.

This is by design. GrowthPicks exists to enforce discipline, not to chase momentum.

This guide is part of the GrowthPicks Toolkit. It is educational content and does not constitute financial advice.