How profit margin is calculated
Profit margin answers one question: of every dollar a customer pays you, how many cents do you actually keep? The formula is simple, but it only works if you feed it every per-unit cost — not just what you paid the supplier.
The costs that most often get forgotten are the small ones that scale with every order: payment processing (typically 2.9% + $0.30 on Shopify), marketplace referral fees (usually 8–15% on Amazon), pick-and-pack charges, and the mailer or box the product ships in. Individually they look trivial. Together they routinely eat 15–25% of the selling price.
Margin vs. markup — the mistake that quietly kills stores
Margin and markup use the same two numbers and give completely different answers. Markup is profit relative to your cost. Margin is profit relative to your price. Suppliers and wholesalers talk in markup; your P&L and your ad platform talk in margin.
| Cost | Price | Markup | Margin |
|---|---|---|---|
| $10.00 | $15.00 | 50% | 33.3% |
| $10.00 | $20.00 | 100% | 50% |
| $10.00 | $40.00 | 300% | 75% |
A seller who hears “keystone pricing is a 100% markup” and assumes that means a 100% margin will price at half of what they intended. If your numbers have ever felt mysteriously worse than your pricing spreadsheet promised, this is the first place to look.
A worked example
Say you sell a kitchen gadget for $34.99. The unit costs $12.50 landed, Shopify plus payment processing takes about $5.25 per order, and shipping the package costs $4.10.
That 37.6% is your ceiling for everything else: advertising, returns, overhead, and — eventually — your own pay. If ads cost more than $13.14 to generate one sale, the product loses money even though the spreadsheet says it is “profitable.” That handoff from margin to ad spend is exactly what the breakeven ROAS calculator is for.
What counts as a “good” margin
There is no universal number, but there are working ranges. Stores that rely on paid traffic generally need 25–40% net margin to survive rising ad costs. Marketplace sellers on Amazon often run 15–25% because the traffic is cheaper and volume higher. Handmade and niche products can sustain 50%+. Below 15%, one refund, one lost package, or one ad-cost spike wipes out several sales’ worth of profit — which is why the calculator flags anything under that line.
FAQ
What is a good profit margin for ecommerce?
After all per-unit costs (product, fees, shipping), most successful DTC stores land between 20% and 40% net margin. Below 15%, paid advertising is usually unprofitable; above 40% you have strong room for ads, discounts and returns. Amazon sellers often operate lower (15–25%) because volume is higher and traffic is cheaper.
What is the difference between margin and markup?
Margin is profit as a percentage of the selling price. Markup is profit as a percentage of your cost. A product that costs $10 and sells for $20 has a 50% margin but a 100% markup. Mixing the two up is one of the most common — and most expensive — pricing mistakes new sellers make.
Should I include shipping in my margin calculation?
Yes, if you pay it. Any cost you incur to get one unit sold and delivered — product cost, platform fees, payment processing, fulfillment, packaging — belongs in the calculation. If the customer pays exactly what shipping costs you, it nets out. If you offer free shipping, that cost is yours and it directly reduces margin.
Does this calculator include advertising costs?
No — deliberately. Ad spend varies per order, so it is usually treated separately as customer acquisition cost. The margin this tool gives you is what is available to spend on ads. To find the ad efficiency you need, use the breakeven ROAS calculator with this margin.
Is my data uploaded anywhere?
No. The calculator runs entirely in your browser with JavaScript. Nothing you type is sent to a server, stored, or tracked.