How to Calculate True Ecommerce Profit Margin (Not Just Revenue)

"Revenue is up" and "we're more profitable" are two different claims, and most sellers only track the first one. A product can sell more units every month while its actual profit shrinks, and a simple sales report will never show you that happening.

What most sellers actually calculate

Ask a seller for their margin and most will do one sum: selling price minus cost of goods. It's the easiest number to reach for, and it's also the one that flatters almost everything, because it leaves out every cost that isn't printed on the supplier's invoice.

The five things missing from that number

• Marketplace referral fees, a percentage taken on every sale, and it varies by category
• Fulfilment and shipping, picked, packed and shipped costs, whether you handle it or the marketplace does
• Advertising spend, specifically the spend that drove that particular sale, not a blended average
• Refunds and returns, allocated back to the product that was returned, not absorbed into a general total
• Storage and holding costs, what it costs to keep the unsold stock sitting on a shelf until it sells

Leave any one of these out and the number left over isn't profit, it's an estimate with an unknown error built in.

The real formula, worked through

True profit per order is revenue, minus cost of goods, minus marketplace fees, minus the ad spend behind that sale, minus shipping, minus the product's share of refunds. Take a product selling at £24.99 with a £9 cost of goods: a 15% referral fee removes £3.75, fulfilment costs £4.20, the ad spend behind that particular sale averages £2.10, and a 6% return rate on that SKU adds roughly £0.90 back as an allocated cost. The naive margin says £15.99. The real one is £5.04, less than a third of it.

Why this number moves every week

Fee tiers change, ad auctions get more expensive, return rates drift with the season. A true profit figure calculated once a month is already out of date by the time anyone reads it. Our /profitability dashboard updates it as orders land, which is what turns this from a monthly exercise into something you can act on while it still matters.

The gap between "revenue is up" and "we're making more money" is exactly this calculation. Most sellers are one spreadsheet formula away from finding out which one is actually true for them. You can /book-a-demo and we'll run it against your own numbers.