Rule of 40 for Manufacturers: Balancing Growth and Profit

The Rule of 40 is a quick test software investors use to judge whether a company is balancing growth and profit. Add the revenue growth rate to the profit margin. If the total is 40% or more, the company is considered healthy.

It was built for software, not for plants. But the question behind it is one every manufacturing owner asks: are we growing in a way that actually makes money and produces cash? I think that question deserves a better tool for a manufacturer, and that's what this post is about.

Below I'll explain the Rule of 40 as software companies use it, why it gives a misleading answer for a $3M to $30M manufacturer, and the version I'd use instead: growth plus EBITDA margin, checked against how much of that EBITDA turns into cash. All examples are illustrative.

What Is the Rule of 40?

The rule is simple. Revenue growth rate plus profit margin should equal at least 40%.

It's usually credited to venture investor Brad Feld. Fred Wilson wrote it up in 2015 on his blog as "your annual revenue growth rate + your operating margin should equal 40%" (AVC, The 40% Rule). Since then, people have plugged in different profit measures: operating margin, EBITDA margin, or free cash flow margin.

The idea is a trade-off. A software company growing 50% a year can lose 10% and still pass. One growing 10% needs a 30% margin to pass. Growth and profit can substitute for each other, as long as the total holds.

Here's how the math looks for three illustrative software companies:

Company	Revenue growth	Profit margin	Score
Fast grower	55%	-10%	45
Balanced	20%	22%	42
Mature	8%	25%	33

The score is a scoreboard, not a plan. It tells you whether the balance is off. It doesn't tell you why.

Why the Rule of 40 Works for Software

The rule makes sense for software because of how software economics work. Once the product is built, selling one more subscription costs very little. Gross margins are high. Revenue renews every year if customers stay.

So a software company can spend heavily on sales today, show a loss, and expect that revenue to keep paying for years. Growth today is a claim on profit later. That's why investors are willing to trade margin for growth, one point for one point.

That logic depends on two things: cheap incremental cost and recurring revenue. A manufacturer usually has neither.

Why the Rule of 40 Doesn't Fit a Manufacturing Plant

I wouldn't use 40 as a target for a plant. Here's why.

Growth eats cash before it makes cash

When a manufacturer grows, it buys more material, carries more inventory and waits longer on more receivables. That cash goes out months before the customer pays. Growth in a plant is often cash-negative for a while, even when it's profitable on the P&L.

Capacity comes in steps

Software can add customers without adding servers in a big way. A plant can't. At some point growth means a new machine, a second shift or more floor space. That's a capital decision, and the Rule of 40 doesn't see it at all.

Margins are structurally lower

Material, direct labor and overhead sit in cost of goods sold. A healthy manufacturer can run very different gross margins from a software company. Holding a plant to a software scale of profit tells you nothing useful.

Revenue isn't recurring in the same way

Many manufacturers have repeat customers, but not contracts that renew automatically. A big program can end. A customer can resource a part. Growth from one strong year doesn't carry forward the way subscription revenue does.

Price can inflate growth

If you passed through a tariff or a steel increase, revenue went up without a single extra part shipped. That's not growth in volume. A growth number that mixes price and volume can make a flat year look like a good one.

For all of these reasons, a manufacturer can score well on the Rule of 40 and still be short on cash. That's the gap I want to close.

The Manufacturer Version: Growth Plus EBITDA Margin

The part of the Rule of 40 I like is the balance. Growth alone isn't the goal, and margin alone isn't either. So I keep the first half of the idea and change the inputs.

Step one is growth plus EBITDA margin. EBITDA is earnings before interest, taxes, depreciation and amortization. It's a rough view of operating profit before financing and before the non-cash depreciation charge. Lenders and buyers use it a lot, so it's a fair common language.

Three adjustments make this more honest for a plant:

• Split growth into price and volume. If revenue grew 12% and 7 points came from price increases, real volume growth was closer to 5%. Show both.
• Use normalized EBITDA. Take out one-time items like a lawsuit settlement or an owner's personal expense run through the business. Don't take out costs that will happen again.
• Use a trailing twelve months. Plants have seasonal swings. A single quarter can mislead.

I don't know of a published target for this sum that I'd trust for $3M to $30M manufacturers. So I don't set one. I'd compare the number to your own last three years and to what your lender and your plan expect. The trend matters more than the total.

The Second Test: Cash Conversion

This is where a manufacturer really needs a second number. EBITDA isn't cash. It ignores the inventory and receivables growth takes, and it ignores the equipment you bought.

So I pair the score with cash conversion. For this purpose I define it as free cash flow divided by EBITDA. Free cash flow here is EBITDA minus the increase in working capital (receivables plus inventory minus payables) minus capital spending. I keep interest, taxes and owner distributions out of it so you can compare years cleanly, then look at those separately.

If cash conversion is high, profit is turning into money in the bank. If it's low or negative, growth or capex is soaking it up. Neither is bad by itself. You just want to know which one is happening, and whether you planned for it.

The cash side ties to your cash conversion cycle, which is the number of days cash is tied up between paying suppliers and collecting from customers. A longer cycle means more cash absorbed by each dollar of growth.

A Worked Example: Two Plants with the Same Score

Here are two illustrative manufacturers. Both had $10.0M of revenue last year.

	Plant A	Plant B
Revenue this year	$11.5M	$10.6M
Revenue growth	15%	6%
EBITDA	$1,380k	$2,120k
EBITDA margin	12%	20%
Growth + EBITDA margin	27	26
Increase in receivables	$400k	$50k
Increase in inventory	$600k	$50k
Capital spending	$300k	$400k
Free cash flow	$80k	$1,620k
Cash conversion (FCF / EBITDA)	6%	76%

The math for Plant A: $1,380k minus $400k minus $600k minus $300k is $80k. For Plant B: $2,120k minus $50k minus $50k minus $400k is $1,620k.

On the growth-plus-margin score, these two plants look the same. On cash, they're nowhere close. Plant A grew fast but kept almost none of its profit as cash. Plant B grew slowly and threw off a lot of cash.

Which one is healthier? It depends. If Plant A's inventory build is for a signed program that ships next quarter, it may be fine. If the inventory is slow-moving or the receivables are aging, it isn't. Plant B could be under-investing and losing share. The numbers tell you where to ask.

How to Read the Four Combinations

Once you have both numbers, there are four basic patterns.

High score, high cash conversion

Growing, profitable and cash-generating. This is where you want to be. The main risk is complacency on pricing and capacity.

High score, low cash conversion

The P&L looks good but cash is tight. This is the classic growth trap. Look at inventory, receivables and whether capex was planned. Your growth and cash flow plan matters most here.

Low score, high cash conversion

Slow and steady. Often a mature business with older equipment. Fine for cash today. The question is whether you are investing enough to stay competitive in three years.

Low score, low cash conversion

This is the one to act on. Margin is thin and cash isn't coming in. Start with pricing and cost by product and customer, and build a short-term cash forecast so there are no surprises.

How Lenders and Buyers Look at Growth and Profit

For a software company, the Rule of 40 is aimed at venture investors. For an established manufacturer, the people judging you are usually different: your bank, a private equity buyer, a minority partner, or you, planning your own exit.

Lenders care most about cash available to service debt. They look at EBITDA, then at what's left after capex, taxes and distributions. That's why debt service coverage matters more to your bank than a growth score.

Buyers look at normalized EBITDA, how steady it is, and how much capital the business needs to keep running. A plant that needs heavy capex every year to hold revenue flat is worth less than one that doesn't, at the same EBITDA. Cash conversion is a simple way to show that.

If you plan to sell in a few years, I'd start tracking both numbers now. Three years of clean history is much more convincing than one good year.

How to Improve the Balance

If the score is low, you have two dials: growth and margin. If cash conversion is low, you have a third: working capital and capex.

To improve margin

Know your margin by product and by customer, not just in total. Reprice work that doesn't cover its true cost. Look at scrap, rework and overtime, which often hide in overhead. Our pricing and margin analysis work starts here.

To improve growth

Grow where margin is already good. Ten percent more of a low-margin part can make the score worse on cash. Check capacity before you say yes to a big order.

To improve cash conversion

Tighten collections. Review inventory for slow movers. Negotiate supplier terms where your volume gives you room. Time capex to the cash plan, and match the financing to the life of the asset. Our working capital guide goes deeper on each of these.

Common Mistakes with Growth and Profit Scores

• Using a single month or quarter. Use trailing twelve months.
• Counting price increases as growth. Separate price from volume.
• Using adjusted EBITDA that adjusts too much. If a cost comes back every year, it isn't one-time.
• Ignoring cash. A good score with poor cash conversion is a warning, not a win.
• Comparing to software benchmarks. A plant and a software company aren't built the same way.
• Reporting it without monthly closes you trust. If inventory and accruals are only right at year-end, so is the score.

For outside reference points, our post on financial benchmarking for manufacturers covers where to find comparison data and how to use it carefully.

How Accounovation Helps

We work as the finance team for established manufacturers between about $3M and $30M in revenue. As part of our fractional CFO work, we build a monthly view of growth, margin and cash conversion, so you can see the balance before your banker or a buyer does.

That sits on top of a clean monthly close and a rolling cash forecast. If cash is the tighter constraint, our cash flow management work is the place to start. Happy to jump on a call if helpful.

Frequently Asked Questions

What is the Rule of 40?

It's a software-industry test where revenue growth rate plus profit margin should total at least 40%. It measures whether a company is balancing growth and profit.

Should a manufacturer use the Rule of 40?

Not as a target. The idea of balancing growth and profit is useful, but plants have lower margins, capacity steps and working capital needs that software doesn't, so 40 isn't a meaningful bar.

What should a manufacturer track instead?

I'd track growth plus EBITDA margin, with price and volume split, and pair it with cash conversion (free cash flow divided by EBITDA). The second number shows whether profit is turning into cash.

What is a good cash conversion rate?

It depends on whether you are growing and investing. Low conversion during a planned growth year can be fine. Low conversion with flat sales usually points to inventory, collections or capex problems.

Do lenders use the Rule of 40?

Not for a manufacturer, in my experience. Banks focus on EBITDA, debt service coverage, covenants and your borrowing base.