Rule of 40: Comparing Software Growth and Profitability
For educational purposes only; not investment advice.
Direct answer
Section titled “Direct answer”The Rule of 40 is an informal software-industry screening convention:
Rule of 40 score = revenue growth rate + stated profit margin
A score near or above 40% is commonly described as balancing growth and profitability, but 40 is not an accounting standard, economic law, valuation, or pass/fail boundary. The score is meaningless unless the period, growth definition, and margin are stated. Common margin choices include GAAP operating margin, adjusted operating margin, or free-cash-flow margin; they are not interchangeable.
Making the score comparable
Section titled “Making the score comparable”Use the same period in numerator and denominator, usually trailing-12-month or fiscal-year revenue growth with the matching annual margin. Separate reported from organic growth by disclosing acquisitions, disposals, currency, and accounting changes. A low prior-year base or an extra fiscal week can distort growth.
For FCF margin = free cash flow / revenue, define free cash flow and reconcile it to operating cash flow and capital expenditure. Customer prepayments, contract liabilities, delayed payables, capitalized commissions, restructuring, acquisitions, and tax timing can make one year’s cash margin unrepresentative.
For adjusted margins, begin with GAAP and show every exclusion. Stock-based compensation is noncash in the cash-flow statement but transfers value through dilution and repurchases; excluding it from profit while ignoring share growth overstates shareholder economics. Compare revenue and cash flow per diluted share as well as company totals.
The rule adds growth and margin with equal weight, although a point of growth is not economically identical to a point of margin. Growth requires retention, acquisition spending, infrastructure, and working capital; assess gross margin, customer concentration, remaining obligations, retention definitions, sales efficiency, and reinvestment.
One company, three scores
Section titled “One company, three scores”Assume current revenue is $500m, up 28%, free cash flow is $75m, GAAP operating loss is $20m, and management reports adjusted operating income of $100m after exclusions:
| Profit definition | Margin | Rule of 40 score |
|---|---|---|
| Free cash flow | 15% | 43% |
| GAAP operating income | -4% | 24% |
| Adjusted operating income | 20% | 48% |
All three calculations are arithmetically correct, but they answer different questions. If free cash flow benefited from a $30m increase in customer prepayments and adjusted income excluded $50m of stock compensation, the headline scores need reconciliation. If diluted shares also rose 6%, total revenue growth of 28% translates to roughly 20.8% revenue growth per diluted share (1.28 / 1.06 - 1) before other share-timing effects.
The next step is not choosing the highest score. Normalize working capital, review exclusions, separate organic growth, examine retention and unit economics, and compare the same definition across peers and years.
Comparison checklist
Section titled “Comparison checklist”- Label fiscal year, trailing period, constant-currency, organic, and acquisition contributions.
- State the exact profit or cash-flow numerator and reconcile non-GAAP measures to GAAP.
- Reconcile operating cash flow to FCF, including capital expenditure, capitalized software, leases, and acquisitions.
- Normalize customer prepayments, receivables, payables, commissions, restructuring, taxes, and one-time collections.
- Track stock compensation, diluted share count, option overhang, and repurchases together.
- Examine gross margin, retention methodology, customer concentration, contract duration, remaining obligations, and churn.
- Distinguish price increases, seat or usage growth, new customers, acquisitions, and accounting changes.
- Compare firms with similar business models, maturity, hosting costs, sales channels, and margin definitions.
- Use multiple years and stress growth deceleration, margin expansion, reinvestment, and dilution.
- Evaluate valuation and balance-sheet risk separately; the score contains neither.
Common misconceptions
Section titled “Common misconceptions”- “Above 40 means the company is good or cheap.” The score does not measure valuation or risk.
- “Every percentage point is equivalent.” Growth and margin have different durability, capital needs, and value.
- “FCF margin is automatically the cleanest choice.” Billing timing and working capital can move it sharply.
- “Adjusted margin is comparable across companies.” Exclusions and definitions differ.
- “Stock compensation can be ignored because it is noncash.” It can dilute ownership or require cash-funded repurchases.
- “The rule applies to every industry.” It was popularized for scalable subscription software and may be uninformative elsewhere.