The calculators estimate seller-side economics in US dollars. They do not predict whether an item will sell, how long it will take, or what your marketplace invoice will contain. Record actual costs after the sale.

What the numbers mean

Revenue is sale price plus shipping collected from the buyer. Marketplace-collected sales tax is not your revenue.

Profit is revenue minus purchase cost, seller-paid shipping, packaging, other entered costs, and estimated seller fees.

ROI is profit divided by cash invested in purchase cost, shipping, packaging and other costs. The calculator excludes seller fees from that investment denominator because they are deducted from the proceeds. If the investment is zero, ROI is undefined rather than infinite.

Margin is profit divided by revenue. Zero revenue leaves margin undefined. ROI and margin use different denominators; a 50% ROI does not imply a 50% margin.

Break-even is the minimum modeled sale price that covers the entered costs. Maximum buy cost works backward from an expected sale and your chosen dollar-profit or ROI target. A negative maximum means the expected proceeds cannot cover the other costs and target, even with a free item.

Marketplace sources

Sources checked 2026-10-03 for United States. Recheck for your category and account before relying on a preset.

  • Ebay official fee guidance: US non-Store most-category estimate: 13.6% through $7,500 and 2.35% above it; $0.30 order fee through $10, $0.40 above. Includes buyer-paid shipping and entered marketplace-collected tax in the fee base. Category, Store, ads and account charges vary.
  • Mercari official fee guidance: US seller estimate: 10% of item price plus buyer-paid shipping for listings using the fee structure effective January 6, 2025. Enter optional transfer, return or other charges separately.
  • Poshmark official fee guidance: US item price: $2.95 below $15; 20% at $15 or above. Enter seller-paid shipping discounts, fee tax and other charges separately. Editing fee fields switches to Custom. Buyer-paid Poshmark postage is not seller revenue; enter only shipping discounts or other shipping costs you bear.

Costs that need your attention

Rates vary by country, category, seller plan, promotions, account status and transaction type. The eBay preset includes an entered sales-tax amount in its fee base without adding it to seller revenue. It models the common US non-Store category tier, not every category.

Enter advertising costs, shipping discounts, fee taxes, listing charges, returns, transfer charges and other applicable expenses yourself. Do not double count a shipping label already entered as seller-paid shipping. Time, unsold inventory and income taxes are not automatically modeled.

A hypothetical example

A $40 sale with $10 purchase cost, $5 seller shipping and $0.75 packaging, using a flat 10% seller fee with no fixed charge, produces $20.25 estimated profit. Cash invested is $15.75, giving about 128.6% ROI and 50.6% margin. This is an example of the method, not a typical outcome or a buying recommendation.

Verification process

The review date above records when these linked sources were checked. Marketplace fees can change and can differ by category, account or transaction. Compare the preset with your current seller charges and use Custom to enter your own assumptions.

Open the resale calculator or contact support if an assumption needs review.

Poshmark buyer-paid postage is not credited as seller revenue in the preset. Enter any shipping discount or extra shipping charge you bear as seller shipping or Other costs. Poshmark shipping guidance explains that buyers pay for postage.