Calculating ROI on Marketing Spend: A Guide

To calculate ROI on marketing spend, subtract what the marketing cost from the profit it earned, then divide the result by the cost. The harder part is knowing how much of that profit the marketing actually caused. This guide covers both the arithmetic and the measurement behind it.

The basic calculation

Marketing ROI compares the return from your marketing with what you paid for it. Take the profit attributed to the marketing, subtract the cost of the marketing, and divide by that cost. A positive result means the spend earned more than it cost. A negative result means it did not.

Use profit rather than revenue wherever you can. Revenue ignores the cost of the products sold, delivery, returns and payment fees, so a campaign can look healthy on revenue and still lose money. Include the full cost of the marketing too: ad spend, agency or freelancer fees, creative production and the tools you use to run it.

Why attribution can mislead you

The simple formula depends on a number that is hard to get right: how much profit the marketing earned. Ad platforms report the sales they claim credit for, and several platforms can claim the same sale. Add those reports together and the total often exceeds what the business actually sold.

Some of those customers would have bought anyway. They were already loyal, or they searched for your brand after hearing about it elsewhere. Counting their purchases as a return on ad spend flatters the channel and hides where money is being wasted.

Measuring what the spend actually caused

Incrementality is the extra sales or conversions your marketing causes that would not have happened without it. Calculating ROI on incremental profit, rather than on all attributed profit, gives a figure you can trust when deciding where to put the next dollar. Seeda has a guide that defines incrementality in marketing and explains how to measure it.

Two approaches are common. Incrementality testing compares a group that sees your marketing with a group that does not. Marketing mix modelling uses historical sales and spend data to estimate what each channel contributes, and it works without tracking individual people, which matters as third-party cookies fade. Seeda’s platform offers marketing mix modelling, incrementality testing, channel-level ROI and budget optimisation.

Putting the result to use

A single ROI figure for all marketing hides the differences between channels. Calculate it per channel, and over a period long enough to capture delayed purchases. Some channels build demand slowly, so a short window can make them look weaker than they are.

Once you have channel-level ROI on incremental profit, use it to shift budget. Move spend away from channels that return less than they cost and towards those that return more, then measure again. Treat the figure as a guide that you keep refining, not a verdict you calculate once.

Frequently asked questions

What is the formula for marketing ROI?

Subtract the cost of the marketing from the profit it earned, then divide by the cost. Express the result as a percentage or a ratio. A positive result means the marketing earned more than it cost.

Should I use revenue or profit?

Use profit wherever you can. Revenue does not account for product costs, delivery, returns or fees, so it can make a loss-making campaign look successful.

Why does the ROI shown in my ad platform differ from my real results?

Platforms report the sales they claim credit for, and more than one platform can claim the same sale. They also count customers who would have bought anyway. Measuring incrementality gives a truer picture of what the spend caused.