C4 · Economics & metrics · heuristic

Rule of 40

Also: Rule of 40

Definition. Rule of 40 adds a stated annual growth rate and a stated profitability margin, in percentage points; 40 is a practitioner threshold. Revenue-growth and ARR-growth variants, and FCF-, EBITDA- or operating-margin variants, must be labeled. Different variants are not interchangeable. It omits runway, unit economics, growth durability and risk.

practitioner heuristic — thresholds do not establish value creation Last updated 2026-06-18 Source: Historical practitioner framework popularized around 2015. Below are score bands for orientation, not verified current market quantiles.

Formula

Rule of 40 heuristic

R_{40} = g_{%} + m_{%}

Plain English: Rule of 40 score = stated annual growth % + stated profitability margin %

Notation: R40 = g_% + margin_%; specify revenue or ARR growth, period, and FCF/EBITDA/operating margin convention

Benchmark by stage

Source: Historical practitioner framework popularized around 2015. Below are score bands for orientation, not verified current market quantiles.

Stage	Rule of 40	Notes
Below conventional threshold	< 40	Heuristic score only; investigate growth quality, margin definition and cash needs.
Meets conventional threshold	40–60	Does not establish sustainable growth or a favorable investment return.
Higher score	> 60	A descriptive band, not a verified current top-quartile boundary.
Very high score	> 80	Inspect measurement definitions and persistence rather than infer market power.

Naive vs corrected

Version	Formula
Naive	Comparing scores that use different growth or margin definitions, or treating a score of 40 as proof of sustainable value creation.
Corrected	Label growth and margin definitions and use comparable periods. FCF and EBITDA answer different questions; FCF does not automatically charge the economic cost of stock-based compensation. Inspect cash runway, contribution economics and forecast risk separately.

Common errors

Mixing growth or profitability definitions across companies
Using decimal growth with percentage-point margin
Treating identical scores as identical cash needs or risk
Applying a public-SaaS valuation heuristic as a universal early-stage target
Assuming a score determines the causal return to incremental investment

Where this sits

Part of the Economics & metrics (C4) cluster in the GTM World Model. Related to the model's "R40=g_%+margin_%. It describes a line in a growth–profitability plane, not a causal production frontier. With matching margin and growth definitions, Rule of X replaces the growth coefficient 1 by a stated X." equation.

arr →burn multiple →rule of x →magic number →

How to cite this

@misc{shalvi_gtm_metric_rule_of_40_2026,
  author = {Singh, Shalvi},
  title  = {Rule of 40 — GTM World Model Metrics},
  year   = {2026},
  url    = {https://shalvisingh.com/gtm/metrics/rule-of-40}
}

Singh, Shalvi. "Rule of 40 — GTM World Model Metrics." shalvisingh.com, 2026. https://shalvisingh.com/gtm/metrics/rule-of-40