How our valuations work
What the AI estimate and the calculator are based on, what they assume, and where they can go wrong.
Last reviewed 3 October 2026
In short: our price estimates come from an AI model's general knowledge of second-hand prices. They are not based on live sold listings or a database of comparable sales. Treat them as a starting point and check recent sold prices before you rely on one — especially for anything valuable, rare or damaged.
Where it works
Estimates and fee calculations cover the United Kingdom (£) and the United States ($) only. Prices aren't converted between currencies — if you switch market, scan again.
How the AI estimate works
- Your photo is resized on your device and sent, with the condition you choose and any notes, to Google's Gemini AI model.
- The model identifies the item as specifically as it can and estimates what similar items typically sell for second-hand in the market you chose.
- We check the answer is complete and consistent (for example, that the likely sale price sits inside the range) before showing it.
What it does not use
- No live marketplace listings, sold-listing feeds or search results.
- No database of comparable sales.
- Not the price you'd pay — that's never sent, so it can't anchor the estimate. Profit is calculated on your device.
What the result means
- Identification confidence — how sure the model is about what the item is. It says nothing about how accurate the price is.
- Price range — a rough range for similar items in the assumed condition.
- Likely sale price — the price a buyer might realistically pay. This is the figure we use for profit.
- Suggested listing price — a higher asking price that leaves room for offers.
- Price uncertainty — the model's own view of how unsure the estimate is. "High" means treat it with extra care.
- Demand — a rough guess only. We don't predict how quickly something will sell.
Condition
A photo can't show whether something works, is complete, or has hidden faults. The model is told to value the item in the condition you report — including faults, missing parts and items that don't work — even if it looks fine. If you choose "Not sure", it doesn't assume good working order: it says what it assumed and widens the range.
Known limitations
- It can misidentify items, especially from one photo, without a label, or for lookalike models.
- It can't confirm authenticity. Fakes of popular brands can look convincing — we never state that an item is genuine.
- Second-hand prices change with trends, seasons and supply; the model's knowledge isn't live.
- Rare, vintage, niche, collectable or damaged items are much harder to price.
- Listing titles and descriptions are drafts. Replace placeholders such as [size] or [tested/untested] with real details and describe condition honestly.
How to check a price yourself
- eBay: search for the item and tick Sold items in the filters. Compare the same model in similar condition, and ignore unusually high or low results.
- Vinted and Depop don't offer an equivalent public sold-items filter. Items marked sold in sellers' shops can help, but cross-check with eBay.
- A displayed sold price isn't always what the buyer paid. When a seller accepts a Best Offer on eBay, the listing can show the original price rather than the accepted offer. Prices may also include or exclude postage, or relate to a bundle.
Our guide to checking sold prices goes into more detail.
How the calculator works
All calculations run in your browser:
- Revenue = sale price + postage the buyer pays you (where postage goes through the seller). Sales tax is never counted as your revenue.
- Fees = the marketplace's seller fees for that sale. Where a marketplace charges its fee on sales tax it collects (eBay US, Depop US), we include the tax in the fee base using the rate you enter.
- Proceeds = revenue − fees − your postage cost − other costs. This is what you'd keep for something you already own.
- Profit = proceeds − purchase price. ROI = profit ÷ (purchase price + other costs).
- Break-even = the lowest sale price that covers every cost. If fees make that impossible (for example a custom fee of 100%), we say so.
- Max buy price to double your money = the most you could pay and still make a 100% return.
Results exclude income tax, the value of your time, promoted listings and boosts, and any fees we list as not modelled below. When you've spent nothing (for example, something you already own), we show proceeds instead of an infinite ROI, and we don't give a buying verdict.
Buying verdict
Strong buy: £/$15+ profit and 200%+ ROI. Worth buying: £/$8+ profit and 100%+ ROI. Marginal: some profit below those levels. Skip it: no profit. These are rules of thumb — the verdict is only as good as the sale price you enter.
Fee sources
| Marketplace | What we model | Source |
|---|---|---|
| eBay UK (private seller) | Free for UK-based private sellers: no final value fee or regulatory fee on domestic sales. UK-based private seller, delivering within the UK. Not modelled: vehicles, international delivery fees, listing fees beyond 300 listings a month, optional upgrades and promoted listings. | eBay UK — Fees for private sellers Reviewed 3 October 2026 |
| eBay UK (business seller) | Final value fee by category on item + postage, plus a per-order fee and 0.35% regulatory fee, with VAT on fees. No eBay Shop subscription, Above Standard seller level, UK delivery. Includes 20% VAT on eBay's fees — VAT-registered businesses may be able to reclaim it. Category bands are simplified to the most common resale categories; check eBay's full table for your exact category. Not modelled: listing/insertion fees, international fee, below-standard surcharges, promoted listings. | eBay UK — Fees for business sellers Reviewed 3 October 2026 |
| Vinted | No selling fee for private sellers — the buyer pays a Buyer Protection fee and postage on top of your price. Private (non-Pro) seller using the Buy now button; the buyer pays postage via Vinted's label. Not modelled: optional Bumps and Showcase, Vinted Pro fees. | Vinted UK — Price List Reviewed 3 October 2026 |
| Depop UK | No selling fee; 2.9% + £0.30 payment processing on item + postage. UK-based seller paid through Depop Payments. Not modelled: 12% boosting fee on Boosted Listings. | Depop Help — Seller fees and charges Reviewed 3 October 2026 |
| Facebook Marketplace (local collection) | No fees for local collection paid in cash or by bank transfer. Local collection only. Shipped Marketplace orders have selling fees that aren't modelled here. | No official source confirmed Not verified in our last review |
| eBay US | Final value fee by category (13.6% for most) on item + shipping + sales tax, plus $0.30–$0.40 per order. No eBay Store subscription, Above Standard seller level, US domestic sale. eBay charges its fee on sales tax collected from the buyer; the tax itself is never your revenue. Not modelled: insertion fees beyond your free allowance, international fees, below-standard surcharges, promoted listings. | eBay — Selling fees (US) Reviewed 3 October 2026 |
| Depop US | No selling fee; 3.3% + $0.45 payment processing on item + shipping + sales tax. US-based seller paid through Depop Payments. Not modelled: 12% boosting fee on Boosted Listings. | Depop Help — Seller fees and charges Reviewed 3 October 2026 |
| Poshmark | $2.95 on sales under $15, 20% on sales of $15 or more. The buyer pays for the shipping label. Widely reported US fee structure — we couldn't confirm it against an official Poshmark page in our last review, so check Poshmark's help centre. Fee applied to the item price; shipping is paid by the buyer. | No official source confirmed Not verified in our last review |
| Facebook Marketplace (local pickup) | No fees for local pickup paid in cash. Local pickup only. Shipped Marketplace orders have selling fees that aren't modelled here. | No official source confirmed Not verified in our last review |
Spotted something wrong?
Fees and prices change. If you notice an error, email [email protected] and we'll check it.
