To calculate profit margin is the only way to know if your business is actually making money or just burning itself out chasing revenue. In fact, a lot of small business owners never do this, product by product. They watch revenue climb and assume everything’s fine. But revenue alone doesn’t tell you what’s left in your pocket at the end of the month. It can hide a loss for months at a time.

That’s exactly what happened to a cardboard box manufacturer, a Meriaky client. His revenue tripled in four months: from $15,000 to $50,000 a month. A result most business owners would sign for without hesitation. Except behind that number, a loss had been building quietly, month after month.

Revenue that hides a loss

By the end of March, this client had generated $38,000 in revenue. He had blown past his own targets. And yet he ended up in the red: he’d made $38,000, gone beyond what he expected, but posted a loss. He was down $5,000, and he couldn’t figure out why.

His outlook sums up the problem a lot of entrepreneurs refuse to see. He said he’d rather generate $25,000 and keep $10,000 than generate $50,000 and lose $5,000. To him, that made no sense at all. In other words, producing more is pointless if every order eats a little more into the cash. And that’s exactly what he couldn’t see, because he didn’t have the right numbers in front of him.

How to calculate profit margin, in practice

To calculate profit margin, on paper, is simple: selling price minus direct costs gives you gross margin. As a percentage, that’s an easy number to track month after month.

The trap is stopping at an overall margin. A business can show a decent average margin while still selling some products at a flat loss. That’s why it pays to calculate your margin product by product, not just at the level of the whole business. You also need to recalculate that margin the moment supplier costs move, because a price locked to a cost that has quietly climbed turns into a losing price without anyone noticing. This calculation ties back to the classic notion of gross margin taught in business school, a benchmark too few owners actually track product by product.

The leaking rice bag

This kind of loss is like running a race with a torn rice bag on your back. Every grain that falls is invisible in the moment. Nobody notices while running, especially when business looks like it’s going well. But at the finish line, the weight of the bag doesn’t lie: there’s a lot more missing than you’d think.

That’s exactly what happened at this box manufacturer. Costs had shifted, quietly, order after order. Prices had stayed frozen for a long time. Without calculating profit margin regularly, nobody could see it coming.

The 36-cent discovery: calculate profit margin order by order

Business owner about to calculate profit margin on a cardboard box order

With an analytics tool Meriaky installed, this client was able to go back through his past orders one by one. That’s where he found the problem, on one specific order: the floor price was $6.56. He had priced it at $6.20, a straight 36-cent loss per unit.

Thirty-six cents is nothing on its own. But multiply it by order volume, and it’s enough to turn a record month into a negative one. This discovery would never have surfaced by looking only at overall revenue, without ever drilling down to individual orders. Calculating profit margin order by order is exactly what brought this hidden number to light.

The real lever: the supplier, not volume

Digging further, a second reality surfaced, an even heavier one: more than 60% of what he generates goes to his sheet supplier. To him, that didn’t add up.

So the real profit lever wasn’t selling more. It was in negotiating with the raw material supplier. Many business owners look for growth on the sales side, when the real margin is often decided on the purchasing side, right where nobody’s looking.

The turnaround in one month

Once the underpricing was fixed and the supplier renegotiated, the numbers flipped fast. March had closed at -$5,000. April ended at +$4,500. Gross margin went from 34% to 54% over the same period, without order volume really changing.

This turnaround isn’t magic. It comes purely from finally looking at the real numbers, product by product, order by order. This is the same client who had Meriaky build him a quoting tool: you can see how that quoting tool was built in the full case study.

Why calculating your profit margin changes everything next

Calculating your profit margin regularly is far more than a bookkeeping task. It’s the only piece of information that tells you whether the month was actually good or bad. Rising revenue can hide a growing loss, while a margin you track closely saves you from a bad surprise at the end of the month.

Bottom line: the question is never how much you sold, it’s how much is left. Want to see where the invisible losses are hiding in your business? Meriaky’s manual task cost calculator gives you a first look in a few minutes.

Frequently asked questions

How do I calculate profit margin simply?

Selling price minus direct costs gives you gross margin. To calculate profit margin as a percentage, divide that result by the selling price, so you get a number you can track easily every month.

Why does my margin drop while my revenue goes up?

Because supplier costs often shift without selling prices following along. So a bigger volume just amplifies a loss that was already sitting on every order.

Should I calculate margin by product or just overall?

By product, because an overall average can hide products sold at a flat loss. That’s usually where the missing money is hiding.

Edouard Vilver, co-founder of Meriaky

About the author

Edouard Vilver · Co-founder of Meriaky

Software engineer with 15 years of experience, including more than 7 years at the National Bank of Canada, where he rolled out electronic signatures and migrated systems to the cloud. Today, he helps small businesses automate their client follow-up and repetitive tasks with AI.

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