Content, tools, and ad spend all cost something real — this works out whether your affiliate marketing is actually paying for itself.
ROI is calculated as (Revenue − Cost) ÷ Cost, expressed as a percentage. A 100% ROI means you doubled your money; a 0% ROI means you broke even; a negative ROI means the campaign or content cost more than it returned.
The part most people get wrong isn't the formula — it's what counts as "cost." Time isn't included here (this is a pure dollar-cost calculation), but if you're spending significant hours on content, it's worth mentally factoring that in separately when deciding whether an approach is actually worth continuing, not just whether it's cash-flow positive.
Should I include my own time as a cost? This calculator deliberately doesn't, since time cost is subjective and varies by what else you could be doing with those hours — but it's worth tracking separately if you want a fuller picture of whether an approach is genuinely worth your effort, not just profitable in cash terms.
What counts as a good affiliate marketing ROI? There's no universal number — it depends on your risk tolerance, how the cost was spent (a one-time content cost that keeps earning for years is different from ongoing ad spend), and what else you could do with that budget.