Marketing ROI tells you whether a campaign generated more value than it cost — a basic question that’s surprisingly easy to calculate wrong if you’re not tracking the right numbers.

The basic formula

Marketing ROI = (Revenue attributed to the campaign minus campaign cost) divided by campaign cost, expressed as a percentage. A campaign that cost $1,000 and generated $4,000 in attributed revenue has a 300% ROI.

The part most people get wrong: attribution

Revenue “attributed” to a campaign isn’t always obvious, especially with multiple touchpoints before a purchase. At minimum, track which channel a customer first discovered you through and which channel drove the final conversion — even that basic split gives you a meaningfully more honest picture than assuming the last click gets all the credit.

Don’t forget the full cost

Ad spend or campaign cost itself
Time spent creating and managing the campaign, valued at a reasonable hourly rate
Any tools or software specifically used for that campaign

Use it to compare, not just report

The real value of tracking marketing ROI consistently is comparing channels and campaigns against each other over time, so future budget goes toward what’s actually working rather than what feels like it’s working.