ROI (Return on Investment) measures how much profit you make relative to your total investment.
Good eBay ROI benchmarks: <20% poor, 20–50% good, 50%+ excellent.
Example: Invest $25 total, sell for $58, net $24.91 profit = 99.6% ROI.
Use this calculator when preparing for a business decision that depends on this metric. Calculating the figure in advance — rather than estimating — prevents the kind of imprecision that leads to suboptimal choices.
The most consequential business calculation error is excluding indirect costs from the calculation. Labour, overhead, and opportunity cost are frequently omitted when evaluating profitability, producing overstated margin figures.
A product manager calculates gross margin for a new product line: manufacturing cost £8.50, proposed retail price £24.99. The calculator returns a 66% gross margin — above the company's 60% threshold, confirming the pricing is viable before taking it to the finance team.
50%+ per item is excellent. Under 20% may not be worth the time and effort.