There's a myth that if sales are growing, profit will sort itself out. It's a comforting thought, a bit like assuming the gym membership is working because you're paying for it.
Plenty of businesses grow revenue every year and keep the same thin profit, or lose ground. The two numbers that explain why are gross margin and net margin, and the gross margin vs net margin comparison is one of the fastest ways to find out which part of your business is leaking.
Here's what each one measures, how to calculate both from your P&L, and what to do when they disagree.
What is gross margin?
Gross margin is the share of each sales dollar left after paying the direct costs of delivering the product or service. Those direct costs are called cost of goods sold, or COGS (for a service business, often labeled cost of revenue or cost of sales).
The formula: (revenue minus COGS) divided by revenue.
What counts as COGS depends on the business. For a product company, it's inventory, freight in and packaging. For a contractor, materials, subcontractors and field labor. For an agency, the people doing billable client work. Rent on the office, the owner's accounting software and the holiday party are not COGS, even though they feel expensive.
Your gross profit margin answers one question: when you sell something, do you make money on that sale before overhead shows up?
What is net margin?
Net margin is net profit divided by revenue. Net profit is the last line of the profit and loss statement, after COGS, overhead, interest and (on a full-year basis) income taxes.
For a small business, net profit margin answers a bigger question: after paying for everything it takes to run the place, what's left?
If your P&L still feels like a wall of numbers, our guide on how to read a profit and loss statement walks through it in about ten minutes.
Gross margin vs net margin: a worked example
Suppose you run a small HVAC service company. Last year's P&L, simplified:
- Revenue: $1,200,000
- COGS (equipment, parts, technician wages, subcontractors): $720,000
- Gross profit: $480,000
- Overhead (office staff, rent, trucks, insurance, marketing, software): $400,000
- Interest on the truck loans: $20,000
- Net profit before taxes: $60,000
Gross margin: $480,000 divided by $1,200,000 is 40%. Net margin (before taxes): $60,000 divided by $1,200,000 is 5%.
Now say revenue grows 20% next year to $1,440,000, but you win that growth by discounting installs and gross margin drops to 34%. Gross profit is $489,600. Overhead creeps up to $430,000 because you added a dispatcher. Same interest. Net profit falls to $39,600, or about 2.8%.
More revenue and more work, for less money. Gross margin explains the first half of that slide and overhead explains the rest.
Which margin tells the real story?
Both do, about different chapters.
Gross margin is the one to watch when you're asking about pricing, job mix, supplier costs or labor efficiency. If it's falling, each sale is getting less profitable, and selling more will only stretch you thinner.
Net margin is the one to watch when you're asking whether the business as a whole is sustainable. If gross margin is healthy but net margin is weak, the problem is usually overhead growing faster than gross profit (the "we hired ahead of revenue" chapter).
A quick diagnostic:
- Gross margin steady, net margin falling: look at overhead.
- Gross margin falling, net margin falling: look at pricing and direct costs first.
- Gross margin rising, net margin flat: overhead is eating the improvement.
Why the margins look wrong when the books are wrong
Margins are percentages, and percentages are only as good as the categories underneath. We see a few repeat offenders.
Direct labor booked to overhead makes gross margin look fantastic and overhead look bloated. Materials bought in December for January jobs, expensed all at once, make December look terrible and January look heroic. Product businesses that record inventory purchases straight to COGS instead of tracking what actually sold get margins that bounce around month to month. Our article on ecommerce inventory and COGS covers that one in detail.
None of these is a disaster to fix. They do mean that if your gross profit margin jumps ten points one month, the first question should be "did something get categorized differently?" before "should we celebrate?" A monthly close that reviews COGS mapping is how you get margins you can compare month to month, and it's a big part of what our financial clarity services are for.
What to do with your margins once you trust them
Track both monthly, on a trailing 12-month basis as well as for the month itself, so one odd month doesn't send you into a spiral.
If gross margin is the problem, pricing is usually the first lever. Our guide to pricing for profit shows how to use your margin numbers to raise prices calmly, with math instead of a stomachache. If net margin is the problem, list overhead by category and compare its growth rate to gross profit's. Whichever grew faster is your conversation.
Questions owners ask
What is a good gross margin for a small business?
It depends heavily on the industry. Software and consulting often run high gross margins, while distribution and construction run much lower. Compare yourself to your own trend first and to businesses with the same model second.
Can gross margin be high and net margin be negative?
Yes. That usually means each sale is profitable but overhead, debt payments or owner costs are larger than the gross profit those sales produce. It's often a volume or overhead problem, not a pricing one.
Is net margin calculated before or after taxes?
Strictly, net margin is after income taxes. Many owners also track a pre-tax version monthly because taxes are settled annually. Your CPA can tell you how taxes will affect the final number for your entity type.
Want the numbers explained in plain English, monthly?
If margins are the kind of thing you'd like to understand without reading a textbook, join The ABFI Accounting Brief. It's practical notes on books, closes and reporting, no market-news filler. And if your margins look strange and you suspect the categories, a consultation is a good next step.