Resale ROI starts with knowing what the sale cost you.

Define what your calculation includes

For this guide, revenue is the item price plus shipping paid to you by the buyer. Item costs are the purchase cost and the direct cash costs of preparing and completing that sale. Item profit is revenue minus those costs. This is a limited per-item view, not your business's final take-home earnings.

Write down your definition and keep it consistent. Some sellers compare profit with purchase cost alone; this example compares it with all the direct item costs listed below. Both denominators can answer questions, but their percentages are different. Label the basis before comparing two results.

Keep more than the purchase receipt

Acquisition and preparation

Record the item's purchase cost and any direct cleaning or repair expense. For a mixed lot, choose and record a reasonable allocation of the shared purchase price so no item's cost quietly disappears.

Selling and payment fees

Use the actual charges on the transaction record when available. Do not apply a remembered fee percentage to every sale; the platform, category, service, or promotion may change the amount.

Postage and packaging

Record the shipping label, box or mailer, and packing materials used. Shipping collected from the buyer is revenue in this example; postage paid is a separate cost. Do not subtract the same postage twice.

Work through one illustrative sale

Item profit = revenue − direct item costs. In this example: $68 − $33 = $35.

ROI on direct item costs = item profit ÷ direct item costs × 100. Here: $35 ÷ $33 × 100 = approximately 106.1%.

That percentage describes this defined calculation. It does not say how quickly the item sold, how much time the work took, or whether the seller's overall business was profitable. If the cost denominator is zero, this formula does not produce a meaningful percentage.

Keep ROI, margin, and dollars separate

Margin uses revenue as its denominator. For the same example, $35 ÷ $68 × 100 is approximately 51.5%. The sale has $35 of item profit, 106.1% ROI on the defined costs, and 51.5% margin. These describe the same transaction from different angles.

A high percentage on a low-cost item can still leave only a few dollars. Keep the dollar result next to the percentage, and record time spent separately if you want to understand how the work fits your schedule.

Update the record after the sale

Before an item sells, label the numbers as estimates. Afterward, replace them with the transaction's actual price and charges. If a refund, return, or extra shipping cost occurs, update the record again instead of leaving the original result unchanged.

This simplified example omits taxes, general overhead, and the value of your labor. It is a bookkeeping illustration, not tax guidance. Keep those considerations separate and visible before treating an item calculation as a complete account of earnings.

Swiftora includes ROI tracking. When using any tracker, check its cost fields and calculation basis against your own records rather than assuming its percentage uses this guide's denominator.