This page explains exactly how the Buy or Pass calculator reaches its numbers. Nothing here is a black box. You should know which figures are real, which are estimates, and how the math is done, so you can trust the verdict or override it.
The calculator answers one question fast. Is this a buy or a pass, before you spend a dollar.
Finding an item. Type it, pick it from the verified list, or scan a photo. The condition toggle sets whether every number below reads as new or used.
Where the numbers come from
The tool pulls from three kinds of sources, and it is honest about which is which.
- The verified list. For a set of common resale categories, the tool ships with real eBay sold medians that we research and refresh. When your item matches one of these, you get a known number, not a guess.
- Photo and text identification. When you scan a photo or type an item name, an AI vision and search model identifies the item, the brand, any emblem or team logo, and the likely size, then estimates a price. This is a starting point, not a verified sold figure.
- Live eBay data. When you tap Get live eBay data, the tool reads eBay directly. Active listing counts and current asking prices come from eBay's official Browse API, so those are exact. Sold counts and sold price ranges come from a grounded web search of eBay sold listings, so those are close estimates. The search is matched to the specific piece: the brand, the emblem or design, the department (mens or womens), and the size when the tool knows them, and always filtered to the condition you are viewing. If a match that specific returns nothing, it loosens step by step but always keeps the brand and the emblem. One caveat: eBay's official feed does not index every listing the website shows, so for a rare item the count can read lower than what you see on eBay itself. The active-count link opens that exact search so you can check.
New versus used
New and used items sell for different prices, so the tool never mixes them.
- A Used or New toggle sits above the photo buttons and again in the verdict. The default is Used. Switch to New for a new item.
- When you scan a photo, the tool looks for attached retail tags. If it sees them, it suggests New. If it does not, it stays on Used. You can always override the toggle.
- New means new with tags or new without tags. Used means pre-owned. The counts, the prices, and the sell-through are all pulled separately for each condition, so a rack of new items never inflates a used price, and worn items never drag down a new one.
- The tool pulls both conditions at once, so switching the toggle is instant and updates every number in the verdict.
Always all-in: price plus shipping
Every comparable sale is read as the buyer's all-in total. That is the item's price plus the shipping the buyer pays. A listing with free shipping counts its shipping as zero, because that seller already built shipping into the one price.
This matters. If you list with free shipping, your single price has to cover the box, the label, and your profit. Reading comps all-in keeps your target honest.
The math in the verdict
The verdict. Net profit, return, and margin sit next to the live eBay read. The sold count is an estimate, the active count is exact, and the number of active listings links straight to that eBay search.
Every figure in the verdict comes from these formulas.
- Net profit equals sale price plus shipping you collect, minus the platform fees, minus your shipping cost, minus what you paid for the item.
- Return on investment equals net profit divided by what you paid for the item, shown as a percent.
- Margin equals net profit divided by the sale price, shown as a percent.
- Break-even sale price is the price at which net profit reaches zero, including the fees at that price.
- Sell-through equals sold divided by sold plus active, shown as a percent, calculated separately for new and used. It is a read on how fast the item moves. A low number means many are listed and few are selling.
The verdict itself is simple. It clears your profit target with strong return, it clears the target, it is thin, or it is a pass.
How fast it will sell
Profit is only half the question. The other half is how long your cash sits tied up in the item. The verdict shows a velocity read for exactly that.
- Daily sales is the market pace, the sold count divided by 90 days. The eBay line shows it as a per-week number, for example about 1.8 sell per week.
- Days to sell is the number of active listings divided by the daily sales pace. In plain terms, it is roughly how long the current competition takes to clear at today's rate, which is a fair proxy for how long an average listing waits. A saturated item with many active listings and few sales shows a long time. A hot item with few listings and steady sales shows a short one.
- The tile pairs that number with a plain badge so you can read it at a glance: Fast is about 14 days or less, Steady is 15 to 45 days, Slow is 46 to 120 days, and Saturated is beyond 120 days. Both new and used get their own read.
Two honest limits. This is built on the estimated sold count, so treat it as directional, not a promise. And it is a market average, so a sharp price and good photos beat the average and sell faster than the number suggests.
Platform fee math
The tool runs the same sale across every platform so you can see which one pays the most after fees. Rates are kept current, and you should still confirm them on each platform before you rely on them. In the math below, item is your sale price and total is item plus any shipping the buyer pays.
| Platform | Seller fee used |
|---|---|
| eBay | 13.25 percent of total, plus 0.40, plus any promoted-ad percent you enter |
| Poshmark | A flat 2.95 under 15 dollars, otherwise 20 percent of the item |
| Mercari | 10 percent of the item, plus 2.9 percent of total, plus 0.50 |
| Depop | 3.3 percent of total, plus 0.45. United States payment processing only, no seller commission |
| Vinted | No seller fees. The buyer pays a separate protection fee |
| Whatnot | 8 percent of the item, plus 2.9 percent of total, plus 0.30 |
| Facebook Marketplace | 5 percent of total, with a 0.40 minimum |
| Custom | Your own percent and fixed fee, for any platform not listed |
What is exact and what is an estimate
| Number | Source | How solid |
|---|---|---|
| Active listing count | eBay Browse API, official | Exact |
| Active asking prices | eBay Browse API, official | Real, current asks |
| Sold count in the last 90 days | Grounded web search of eBay sold listings | Estimate |
| Sold price range, all-in | Grounded web search of eBay sold listings | Close ballpark |
| Days to sell and velocity badge | Active count divided by the estimated sold pace | Directional, inherits the sold estimate |
| Photo identification and estimated price | AI vision and search | Best guess, verify it |
| Verified category medians | Our own eBay sold research | Verified, refreshed over time |
The most reliable read is the active data and the price range. Treat the sold count as directional. If you want a to-the-penny sold history, that requires eBay's Marketplace Insights access, which is a separate step we may add.
The honest summary
Use the verified numbers and the live active data with confidence. Treat the AI price and the sold count as a strong starting point that you confirm before you buy. The tool is built to make you faster and sharper in the aisle, not to replace your own check on a real sold listing.
This is an educational tool, not financial advice.