The Rule of 40 is one of the simplest and most widely quoted benchmarks in software. Add a company's growth rate to its profit margin. If the total is 40% or higher, the company is generally considered to be balancing growth and profitability well. Investors use it to compare very different software businesses on one scale, and boards use it to decide whether to push for faster growth or better margins.
The Rule of 40 for SaaS says revenue growth rate plus profit margin should equal 40% or more. Rule of 40 formula: growth % + margin % = score. For a Rule of 40 calculation, use consistent measures, such as year-over-year revenue growth and free cash flow or EBITDA margin. It's one of several SaaS efficiency metrics investors use alongside burn multiple and net revenue retention.
It's simple, which is its strength and its weakness. This guide explains how to calculate it properly, how investors use it, and where it gives misleading answers.
The formula
Rule of 40 score = revenue growth rate (%) + profit margin (%)
If the score is 40 or above, the company "passes."
Examples (illustrative):
- Company A grows 60% a year with a −20% margin: 60 + (−20) = 40. Passes.
- Company B grows 15% a year with a 30% margin: 15 + 30 = 45. Passes.
- Company C grows 35% a year with a −15% margin: 35 + (−15) = 20. Falls short.
- Company D grows 100% a year with a −50% margin: 100 + (−50) = 50. Passes, despite heavy losses.
The appeal is that it lets you compare a fast-growing, loss-making company with a slower, profitable one. Both can be healthy, in different ways.
Which growth number to use
There's no single standard, so be consistent and state what you used.
- Year-over-year revenue growth is the most common choice.
- ARR growth is often used for subscription businesses, especially private ones that track ARR more closely than recognised revenue.
- Trailing twelve months vs forward: most analyses use the last twelve months. Some investors look at forecast growth, which is useful but less reliable.
Avoid mixing measures, such as forward growth with historical margin, when comparing companies.
Which profit margin to use
This is where the most debate happens. Common choices:
| Margin measure | Pros | Cons |
|---|---|---|
| EBITDA margin | Widely understood; used by many investors | Ignores capitalised software costs and stock-based compensation in some definitions |
| Free cash flow margin | Reflects actual cash generated or burned | Can be distorted by timing of collections, such as annual prepayments |
| Operating margin (GAAP/IFRS) | Includes all operating costs | Stock-based compensation can make it look much worse than cash results |
| Adjusted operating margin | Strips out one-off items | Adjustments vary; easy to flatter |
Many public market investors prefer free cash flow margin. Many private company boards use EBITDA. Whichever you choose, use the same one each period and for every company you compare.
Where the Rule of 40 came from
The idea is generally credited to venture and growth investors observing software companies in the mid-2010s. It caught on because it captured something investors had been doing informally: forgiving losses when growth was high, and expecting profits when growth slowed. It became especially prominent after 2022, when investors shifted sharply from rewarding growth at any cost to rewarding efficient growth.
How investors use it
Public software companies
Analysts often find that public SaaS companies with higher Rule of 40 scores tend to trade at higher valuation multiples. It's not a perfect relationship, but it's strong enough that management teams track it and present it to investors.
Private growth-stage companies
For companies raising Series B and later, the Rule of 40 is a common conversation in diligence. Growth investors use it to judge whether a company's burn is justified by its growth.
Early-stage startups
At seed and Series A, the Rule of 40 is usually not very meaningful. A company growing from $500,000 to $2 million in revenue has 300% growth and probably a very negative margin. The score swings wildly and says little. Early-stage investors care more about retention, product-market fit and the efficiency of early sales. See what VCs look for in a Series A.
A rough rule of thumb many investors follow: the Rule of 40 starts to matter once a software company reaches meaningful scale, often discussed as somewhere above $10 million to $20 million in ARR.
Where the Rule of 40 misleads
It treats growth and profit as interchangeable
A score of 40 from 40% growth and 0% margin is not the same as 0% growth and 40% margin. Most investors value a percentage point of growth more than a percentage point of margin for high-growth companies, because growth compounds. Some investors weight growth more heavily for that reason.
It ignores scale
Growing 60% from a small base is much easier than growing 60% from a large base. The Rule of 40 doesn't distinguish.
It ignores quality of revenue
Revenue from one-off services, a few huge customers, or heavy discounting counts the same as durable recurring revenue. Pair the Rule of 40 with net revenue retention and gross margin to see the full picture.
It can be gamed
Cutting sales and marketing spend boosts margin immediately but may hurt growth later. A single period's score can look good while the business weakens.
It doesn't suit every business model
It was designed for software. Applying it to marketplaces, fintech lenders or hardware companies can mislead, because their margin structures and capital needs are different.
Related efficiency metrics
| Metric | What it measures |
|---|---|
| Burn multiple | Net cash burned divided by net new ARR. Lower is better. |
| CAC payback | Months of gross profit needed to recover the cost of acquiring a customer |
| Magic number | New ARR generated per dollar of prior-period sales and marketing spend |
| Net revenue retention | Revenue growth from existing customers after churn and expansion |
| Gross margin | Revenue minus direct costs of delivering the product |
Investors rarely rely on any single metric. A company that passes the Rule of 40 but has a poor burn multiple or weak retention will still face hard questions.
How to improve your score
There are only two levers, but many ways to pull them:
- Improve growth efficiency: focus spending on the channels and segments with the best payback; cut low-return campaigns.
- Expand existing customers: expansion revenue usually costs far less than new customer acquisition.
- Raise prices where you deliver more value than you charge for.
- Improve gross margin: reduce hosting and support costs per customer.
- Control headcount growth: hire ahead of need only where it clearly drives revenue.
Using the Rule of 40 in your board deck
If you present the Rule of 40, show it over several quarters, state which growth and margin measures you used, and show the components separately. A trend from 25 to 38 tells a more useful story than a single number. Put it alongside burn multiple and retention so the board sees growth, efficiency and durability together.
A worked example over three years
Illustrative SaaS company
| Year | Revenue growth | Free cash flow margin | Rule of 40 score |
|---|---|---|---|
| Year 1 | 85% | −45% | 40 |
| Year 2 | 55% | −20% | 35 |
| Year 3 | 40% | +5% | 45 |
The story behind those numbers is common. In year one, the company spends heavily to grow and just reaches 40. In year two, growth slows faster than margins improve, and the score dips. That's often the moment boards push for efficiency. In year three, the company cuts low-return spending, raises prices and grows existing customers, and the score recovers above 40 with a positive cash margin. Investors reading this trend would want to know whether year three's efficiency gains are durable or came from cutting investment that will hurt growth later.
Rule of 40 for private companies raising money
If you're preparing for a growth round, a few practical points:
- Know your number before investors calculate it. They will, and they may use a different margin definition than you'd choose.
- Show your plan to improve it. A credible path from 25 to 40 over the next 18 months can be more persuasive than a one-off strong quarter.
- Explain investment periods. If you're deliberately spending ahead of growth, for example launching in a new market, say so and show the expected payback.
- Use it as one input, not the headline. Lead with growth, retention and customer evidence; use the Rule of 40 to show balance.
Frequently asked questions
What is the Rule of 40?
A software benchmark that adds a company's revenue growth rate and profit margin. A combined score of 40% or more is generally considered healthy.
Should I use EBITDA or free cash flow margin?
Either can work. Free cash flow margin is popular with public market investors, EBITDA with many private boards. Be consistent and state which you use.
Does the Rule of 40 apply to early-stage startups?
Not very well. It becomes more meaningful once a software company reaches substantial, steadier revenue.
What is a good Rule of 40 score?
40 or above is the traditional benchmark. Scores well above 40 are considered strong, especially at larger scale.
Is the Rule of 40 used for non-software companies?
Sometimes, but it was designed for software and can mislead for businesses with very different margin structures, such as lenders or hardware companies.