The Rule of 40 and Why Most Software Companies Now Fail It

One Number for the Whole Business

Software companies are unusual. For years the best ones grew explosively while losing money and investors had to decide whether that was brilliant or reckless. The Rule of 40 emerged as the simple test that solved the problem. Add a company's revenue growth rate to its profit margin and a healthy software business should reach 40 or more. A company that grows 30 percent with a 10 percent margin gets a score of40 and pass. The same goes for someone who grows 50 percent without losing expenses. The rule captures the central tension of software in a single number: the balance between growth and profitability

Why Growth and Profit Trade Off

The logic is that a software company can almost always achieve more growth by spending more on sales marketing and engineering which crushes its margin. Or it can reduce that spending to increase its margin which slows its growth. Neither extreme is healthy on its own. A company that grows rapidly while losing cash may never reach profitability while a company with wide margins but no growth is quietly dying. The Rule of 40 says that the mix is what matters and that a great business can always lean in either direction.that the two numbers together surpass the bar

A Worked Example: Two Companies That Both Score 40

The core assumption of the rule is that one growth point and one margin point are worth the same. Try it with numbers and it will immediately fall apart

Take two software companies each with 100 million in revenue today and each with an exact score of 40

Company A grows 45 percent annually with a negative free cash flow margin of 5 percent. 45 minus 5 equals 40

Company B grows 15 percent annually with a free cash flow margin of 25 percent. 15 plus 25 equals 40

Keeping both rates constant for five years which is unrealistic in both directions but keeps the arithmetic clean. Company A's revenue compounds at 1.45 to the fifth power which is 6.41 taking it from 100 million to about 641 million. Company B compounds at 1.15 per fifth which is 2.01 reaching about 201 million

Company B has generated about 194 million cash during those five years. Company A has burned about 87 million. On the cash flow statement B looks like a serious business and A looks like a science project

Now value them. Apply the same 5x revenue multiple to both in the fifth year. Company A is worth about 3.2 billion. Company B is worth about 1 billion. Even after subtracting every dollar A burned and adding every dollar B produced A is worth about two and a half times as much

The rule graded them identically. The market wouldn't come close. This isn't a small blemish around the edges it's a factor of two or three in the core issue and it happens because compound growth builds up on a base that keeps growing while a point of margin builds up once and is spent

These are illustrative figures with constant rates and in the real world A's growth declines and B's might not. The direction of the error does not depend on that. Whenever a metric adds two quantities that compound differently it will systematically underestimate the one that compounds faster

Most Companies No Longer Pass

The surprising thing about 2025 is that few companies actually surpass it. Of the 58 SaaS companies actively marketing at the end of 2025 only about 20 percent passed the Rule of 40 and the average score had fallen to just 28. Private software companies looked even worse with an average score of around 12

Why Investors Still Use It

If most companies don't pass the test why do they survive? Because it still separates the winners from the losers. Companies that break 40 consistently trade at significantly higher revenue multiples than those that don't. The rule is less a pass-or-fail gate than a quick read on quality a way to take a look at two numbers and know whether a software company is balancing its growth and profitability or sacrificing one for the other. In an industry where companies are valuedbased on your income rather than your earnings that single check does an enormous amount of work

Case Study: Salesforce and the Year It Bought Its Score

The clearest recent demonstration of the rule's usefulness and weakness is Salesforce in 2023

Salesforce had spent two decades as the archetype of growth-first enterprise software expanding through big acquisitions and big sales spend. By late 2022 growth was slowing toward 10% while margins remained modest putting its Rule of 40 score in unimpressive territory. Several activist investors including Starboard Value Elliott Management and ValueAct built positions and publicly made the argument: the company was spending like ahigh growth company without growing as such

In January 2023 Salesforce announced it would cut about 8,000 jobs about 10 percent of its workforce in addition to office closures and a sharp reduction in hiring. Over the next year non-GAAP operating margin expanded dramatically rising about eight percentage points. Revenue growth continued to slow reaching double digits. The Rule of 40 score improved substantially. The stock nearly doubled during2023

Read one way this is the rule that works exactly as expected. A company was unbalanced the metric said so management rebalanced and the market rewarded it

Interpreted another way it's the clearest example available of the rule's blind spot. Almost all of the score improvement came from the margin side and margin improvement of that kind is finite. You can only cut ten percent of the workforce once. The growth line which is the component part and the part that the example above shows is worth multiples more continued to slow throughout

Both readings are defensible and that's precisely why the result alone can't settle the issue. The number increased. Whether business improved depends entirely on whether the cuts eliminated waste or eliminated future growth and the metric says nothing about that distinction

The AI Wrinkle

The newest challenge is artificial intelligence. AI functions are expensive to run because each query consumes real computing cost putting pressure on the marginal side of the equation even as companies rush to add AI to drive the growth side. The Rule of 40 is becoming a real test of whether AI really pays for itself and whether the growth it generates outweighs the cost it adds. Over the next few years watching how software companies manage that trade-off will be one of the clearest windows into whether the boomof AI is creating real value or just real spending

There is a structural point underneath this. Traditional software had near-zero marginal cost which is the only reason the industry got the margins it did

The Limits of the Rule

Like any number it can be misleading. It treats a growth point and a margin point as equal when investors typically value long-lasting growth more. It says nothing about the quality of revenue how demanding customers are or how big the market is. And you can be flattered during a quarter by slashing investment to increase margin. It's the starting point of a conversation not the conclusion which is exactly how a good analyst treats it

Where the Rule Actively Misleads

Beyond the usual caveats there are three ways in which the Rule of 40 not only simplifies but distorts

No one agrees on what margin to use. Growth is unequivocal. Margin is not. Companies and analysts variously use GAAP operating margin non-GAAP operating margin EBITDA margin or free cash flow margin and the answers differ wildly. The biggest gap is stock-based compensation which many software companies exclude from non-GAAP numbers and which can be as high as 10% as a percentage of revenue. Include it or exclude it and the same company's score movesby more than fifteen points. A metric whose value depends largely on an accounting choice is not a number it is a family of numbers that share a name

It completely ignores the cost of capital. The rule was popularized when money was almost free and a company that burned cash could always raise more. A score of 40 based on 45 percent growth and a negative margin means something completely different with interest rates of 5 percent than with zero because the burn now must be financed at a real price. The threshold never changed. The environment did

Treat dilution as free. If growth is bought with deeply discounted shares issued to employees earnings per share may barely budge while the overall score appears excellent. The rule measures the business and ignores who owns it with shareholders only getting paid for the second

My view is that 40 is a reasonable rating threshold and a bad target and that the industry's attachment to it says something about how much analysts want a single number on a company that doesn't have it

How I Actually Use It

I use the Rule of 40 as a screen and never as a conclusion and I have a short routine for it

First I recalculate the score myself from the free cash flow margin leaving out stock-based compensation because that's the version that corresponds to the money shareholders could actually receive. It's almost always worse than the number listed by investors and the size of the gap is itself informative about how the company likes to be seen

Second I split the score into two parts and look at the trend of each over eight quarters rather than the sum. A score that stays at 40 while growth falls and margin rises is a company in a completely different situation than one that stays at 40 with both stable and the sum hides it completely. Here's the Salesforce question on a chart

Third I ask what would happen to the score if the company stopped cutting. Margin expansion from genuine waste disposal persists. Margin expansion due to underinvestment reverses and reverses at the same time as growth is already slowing

Fourth for anything AI-heavy I specifically look at gross margin rather than operating margin because that's where inference cost shows up first and where old software economics will break down if it is

My honest read on the sector going forward in 2026 is that an average score of 28 is not a temporary dip but rather the sound of a category maturing and that investors will eventually stop rating software against a standard established during its adolescence. That is an opinion and not investment advice

Why It Matters for the Role

The Rule of 40 is a perfect example of how finance turns a messy business into a single number ready to make decisions while still knowing its limits. Understanding why a company rates what it does and whether that rating is based on lasting growth or temporary cost reduction is the type of analysis that separates someone who can rattle off a metric from someone who really understands the underlying business

The Bottom Line

The Rule of 40 adds revenue growth to profit margin and requires 40. In 2025 only about one in five public SaaS companies passed it the median fell to 28 and the collapse was due to a slowdown in growth rather than a deterioration in margins

The rule's own arithmetic shows why it can't be the answer. Two companies with an exact score of 40 one growing 45 percent with a negative 5 percent margin and another growing 15 percent with a 25 percent margin end the fifth year with $641 million and $201 million in revenue respectively. The metric calls them equal. Nothing else does

Salesforce is the case to be reckoned with. It set its score in 2023 by cutting about 8,000 jobs the stock almost doubled and the growth line continued to slow down all the time. Use the rule to decide which companies deserve an afternoon of your attention then throw it away and see what's really aggravating