Most profit calculations stop at the sale. Returns are handled as an afterthought — “about 5%” — and then a product that looked like a 30% margin ends up at 20% in the annual accounts. The arithmetic is not hard; it just has to include everything a return actually destroys. This guide builds the number step by step and shows how the four main platforms treat fees on a refund. Fee rules are from the platforms’ public policies, verified 2026-09-20 (data sources).
What one return costs
Take a $30 product: 15% marketplace fee, $9 product cost, $4.50 outbound shipping. A normal order nets $12.00.
When it comes back, the sale is reversed — the $30 goes back to the buyer — and these costs stay with you:
| Cost | Amount | Why |
|---|---|---|
| Outbound shipping | $4.50 | Already paid; not refunded by anyone |
| Advertising that produced the order | $0 here (add your ACoS × price if you run ads) | The click was paid whether the sale sticks or not |
| Fees the platform keeps | $0.90 | Amazon keeps 20% of the $4.50 referral fee as a refund administration fee |
| Return postage | $4.50 | Under most free-returns policies you pay the return label |
| Product not resellable as new | $2.70 | If 30% of returns cannot be resold, that is 30% × $9 |
| Loss per returned order | $12.60 | More than the profit of a normal order |
One return wipes out the profit of one normal order — and a little more. That ratio (loss per return ÷ normal profit, here 1.05) is the single most useful number to know about a product.
From return rate to expected profit
Expected profit per order = (1 − return rate) × normal profit − return rate × loss per return.
| Return rate | Expected profit | Expected margin |
|---|---|---|
| 2% | $11.51 | 38.4% |
| 5% | $10.77 | 35.9% |
| 8% | $10.03 | 33.4% |
| 15% | $8.31 | 27.7% |
| 25% | $5.85 | 19.5% |
| 30% | $4.62 | 15.4% |
The break-even return rate — where expected profit reaches zero — is normal profit ÷ (normal profit + loss per return) = 12.00 ÷ 24.60 = 48.8%. Comfortable for a kitchen gadget; not for a dress with a 30% return rate and a lower margin. At a 20% margin (product cost $15 instead of $9) the same product breaks even at about 30% returns.
How each platform treats fees on a refund
| Platform | What you get back | What you lose |
|---|---|---|
| Amazon (FBA) | Referral fee minus the refund administration fee ($5 or 20% of the referral fee, whichever is less) | The FBA fulfillment fee; return postage on Amazon’s prepaid label for most categories; unsellable units are disposed of or returned to you for a fee; in high-return categories, a returns processing fee per unit |
| eBay | Final value fee credited on a full refund; proportional credit on partial refunds | The per-order fee ($0.30/$0.40); return postage if your policy is free returns or the return is “not as described” |
| Etsy | Transaction fee credited on refund | Listing fee; return postage per your shop policy; Offsite Ads fee may be credited only when the refund is issued within the attribution window — check the current policy |
| Shopify Payments | The refund itself — nothing else in most countries | The card processing fee is generally not returned (varies by country); return postage per your policy; app-based return labels |
Sellers whose numbers matter most: apparel on Amazon (high rate, FBA fee lost, returns processing fee), and anyone paying for traffic on Shopify (the ad spend per order is lost twice — once on the returned order and again on the replacement sale).
Reducing the loss, not just the rate
- Resellable share is the lever with the biggest range. Sealed packaging, size charts and clear photos keep it near 90% for hard goods; it approaches zero for opened cosmetics. Each 10 points of resellable share on a $9 product is worth $0.90 per return.
- Return postage: for low-value items it can be cheaper to refund without return (“returnless refund” on Amazon) than to pay $4.50 to get back a $9 product you cannot resell.
- Price: the calculator’s last column gives the price that restores your original margin at each return rate. For the $30 example, absorbing an 8% return rate takes the price to about $35; a 15% rate to about $42.
- Ads: every point of ACoS is also lost on every returned order, so high-return products should run at a lower target ACoS.
Put your own numbers into the return rate calculator — it builds the loss per return, the expected profit and the break-even rate, and feeds the result into the profit margin calculator for the monthly view.