To track your reselling profit properly, record four numbers for every item: what you paid for it, the fees the platform took, what shipping cost you, and what it sold for. Real profit is sell price − cost − fees − shipping − any expenses. Most resellers only track the first and last number, which is why their "profit" never matches what's actually in the bank.

The number most resellers get wrong

Buy a jacket for £20, sell it for £50, and it's tempting to call that £30 profit. But once the platform takes its cut, you pay to post it, and you factor in the packaging, the real figure is closer to £18–£22. Do that across a few hundred sales a year and the gap between "what I thought I made" and "what I actually made" can be hundreds or thousands of pounds.

This is true whether you flip sneakers, trading cards, vintage clothing, electronics or sealed collectibles. The categories differ; the maths doesn't.

The real profit formula

profit = sell price − item cost − selling fees − shipping − expenses

Each piece matters:

Selling fees (the silent killer)

Every marketplace takes a cut, and they're all different:

eBay charges a final value fee that varies by category, plus a fixed per-order fee.
Depop and Vinted structure fees differently again (and Vinted shifts the buyer-protection fee onto the buyer in many regions).
Whatnot, Mercari, Poshmark, StockX and Etsy all have their own percentages.

If you sell across more than one platform, "fees" isn't one number — it's a different calculation per sale. A profit tracker has to handle that per order, or your totals are wrong.

Shipping

Shipping eats profit in two ways: what you pay to send the item, and any postage you ate to offer "free delivery." Track the actual cost per order, not an average — a heavy item can wipe out the margin a light one earned.

Expenses

The costs that aren't tied to a single sale still come out of your profit: packaging, mileage to the post office, sourcing trips, subscriptions, storage. Serious resellers log these as expenses so the year-end profit number is honest.

Why a spreadsheet starts to creak

A spreadsheet is fine for your first 20 sales. Past that it tends to break down:

Per-platform fee formulas get copied wrong and silently corrupt your totals.
You forget to log shipping on busy days, so margins look better than they are.
There's no easy way to see "what's still unsold" versus "what actually sold."
Multi-quantity buys, partial refunds and returns turn into a formula nightmare.

The data is all there — it's just not trustworthy anymore.

What to track per order — the checklist

For every item, capture:

Item / title — what it is
Cost — what you paid to acquire it
Date bought and source/retailer — where it came from
Platform — where you listed it
Sell price and date sold
Fees — the platform's cut for that sale
Shipping — what postage cost you
Status — pending, listed, sold, returned

With those eight fields you can answer the only questions that matter: what did I actually make, on what, and where?

Bring every platform into one place

The reason cross-platform tracking is painful is that your sales live in eight different apps that don't talk to each other. The fix is one place that understands reselling — orders, fees, shipping and real profit in a single view, across whatever platforms you sell on, in your own currency, with your own retailers and brands.

That's exactly what we built Reseller OS to do. It's a desktop app, so your numbers stay on your machine — no account, no cloud. You add the platforms, retailers and categories you actually use, and it does the per-order fee and profit maths for you.

Want it? Join the waitlist — it's free through the beta, and you get a spot in the Discord.

Track the right four numbers per order, and "profit" stops being a guess.