This one mistake costs small contractors real money on every single job they run. I'm not exaggerating. If you're confusing markup and margin — and most people in the trades are — you're systematically undercharging, and the gap between what you think you're making and what you're actually making grows with every job.
It's not complicated once you see it clearly. But it's easy to miss because both numbers sound like they're telling you the same thing.
The difference, as clearly as I can put it
Markup is a percentage added to your cost to arrive at your price. If your total job cost is $10,000 and you mark it up 25%, your price is $12,500. The $2,500 is 25% of your cost.
Margin is what percentage of your final price is profit. On that same $12,500 job where your cost was $10,000, your profit is $2,500. But $2,500 is only 20% of $12,500 — not 25%.
Here's where the mistake happens: a contractor says "I want to make 25% on this job" and adds 25% to their costs. But they haven't made 25% — they've made 20%. They confused markup with margin. Over the course of a year, that difference adds up to a lot of money left on the table.
The formula to get to the margin you actually want
If you want a specific gross margin percentage, here's how to calculate the markup to apply to your costs:
Markup % = Desired Margin % ÷ (1 − Desired Margin %)
So if you want a 25% margin:
Markup = 0.25 ÷ (1 − 0.25) = 0.25 ÷ 0.75 = 0.333, or 33.3%
A 25% margin requires a 33.3% markup on your costs. Not 25%.
Let's run through a few common margin targets so you can see the pattern:
- Want 15% margin → apply 17.6% markup
- Want 20% margin → apply 25% markup
- Want 25% margin → apply 33.3% markup
- Want 30% margin → apply 42.9% markup
Most small contractors are targeting 20% margin and applying 20% markup — which means they're actually running at 16.7% margin. On a $50,000 revenue month, that's $1,650 in profit they thought they were making but weren't.
Why it matters more as jobs get bigger
On a $1,200 job, confusing markup and margin costs you maybe $40. Annoying but not catastrophic. On a $45,000 excavation contract, that same confusion costs you over $1,500. On a big commercial project it can be several thousand dollars of profit you bid away without realizing it.
The larger your jobs, the more precisely this math needs to be right. And since most contractors who stay in business long enough eventually move toward bigger jobs, getting this straight now is worth the 20 minutes it takes to internalize.
What to actually do with this
Decide what gross margin you want to run at. That's a business decision based on your overhead, your risk tolerance, and your market. For most small trade contractors, somewhere between 15% and 25% gross margin is realistic depending on the type of work and how competitive your market is.
Once you know your target margin, calculate the corresponding markup once, write it down, and use that number consistently. Don't redo the math every time — just know your number and apply it.
If you're using estimating software, most of it lets you set a default markup percentage. Set it to the right number — the one that actually gives you your target margin — and leave it there.
It's a small fix that pays you back on every single job from here on out.
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