ROI (return on investment) is the percentage of profit you make on what you invested: it tells you whether an activity made or lost money, and how much relative to its cost.
The ROI formula
The standard formula is:
ROI = (profit − investment) / investment × 100
An ROI of 0% means you got back exactly what you put in. Above zero you make money; below zero you lose it. An ROI of 100% means you recovered the investment and earned the same amount again on top.
The key word is profit. Sales are not profit: from every sale you have to subtract what the product or service costs you (purchasing, production, shipping, fees). Use revenue instead of margin and your ROI will be inflated.
A marketing ROI example
An online store runs a one-month campaign with these numbers:
- Ad spend: €1,500
- Campaign management and tools: €500
- Total investment: €2,000
- Sales attributed to the campaign: €10,000
- Gross margin on the products: 40%
The gross profit on those sales is €10,000 × 40% = €4,000. Applying the formula:
ROI = (4,000 − 2,000) / 2,000 × 100 = 100%
Had you used sales instead of margin, you would get (10,000 − 2,000) / 2,000 × 100 = 400%. Four times more optimistic and simply wrong. It is the most common mistake when calculating campaign ROI. Leaving out management and tool costs has the same effect: with ad spend alone as the investment, the same campaign would show an ROI of 167%.
ROI vs ROAS
ROAS and ROI are often mixed up, but they measure different things:
| ROAS | ROI | |
|---|---|---|
| What it measures | Revenue per unit of ad spend | Profit per unit invested |
| Formula | Revenue / ad spend | (Profit − investment) / investment × 100 |
| Costs included | Ad spend only | Ads, management, tools, product |
| What it is for | Comparing paid campaigns and channels | Knowing whether the investment pays off |
| Example above | 10,000 / 1,500 = 6.67 (667%) | 100% |
A handy way to connect the two: your break-even ROAS on ad spend is 1 divided by your margin. With a 40% margin you need a ROAS of at least 2.5 just to cover advertising, before management and tools. You can run these numbers with the ROAS and ROI calculator.
How to calculate marketing ROI step by step
- Define the scope: one campaign, one channel (SEO, Google Ads, paid social) or all marketing over a period.
- Add up every cost: media spend, agency or freelancer fees, internal hours, tools, creative and content production.
- Choose an attribution rule: which sales you credit to the activity. A last-click model rewards closing channels and penalises the ones that create demand. Pick a rule and stick to it so periods stay comparable.
- Turn sales into profit using your real gross margin per product or service.
- Set a time window that matches your sales cycle. If customers take three months to decide, measuring at 30 days makes no sense.
- Apply the formula and compare with previous periods or other channels.
To track ROI alongside other metrics, add it to your marketing KPIs and follow it in a dashboard that updates itself.
What is a good ROI?
There is no single figure that fits everyone. Any positive ROI means the activity makes money, but the useful question is different: does it return more than the next best alternative? A 50% ROI can be excellent in a low-margin sector and poor in a high-margin one. Factor in customer lifetime value too: if the first purchase barely covers costs but the customer keeps buying for years, first-sale ROI understates reality.
The limits of ROI
- Long sales cycles: in B2B or high-ticket purchases, the sale arrives months after the first touch and is easy to misattribute.
- Brand effects: part of marketing's impact never becomes a measurable sale; it shows up as branded searches, referrals or future direct traffic.
- SEO takes months: organic traffic compounds over time. ROI measured in the first months of an SEO project is almost always negative, even when the investment ends up highly profitable.
- Incomplete data: rejected cookies, in-store purchases and phone calls mean some conversions are never recorded.
Use ROI to decide where to invest, but pair it with process metrics such as CTR, CPC or conversion rate, which tell you what is failing before ROI confirms it.
Frequently Asked Questions
-
ROI (return on investment) measures how much profit you make for every unit of money invested. The formula is ROI = (profit − investment) / investment × 100. If you invest €2,000 and generate €3,000 in gross profit, your ROI is 50%.
-
ROAS divides revenue by ad spend and ignores costs. ROI uses profit and every cost of the activity (ads, management, tools). A campaign can show a high ROAS and a negative ROI if the product margin is thin.
-
Any positive ROI means you get your money back and earn on top. Beyond that there is no universal number: it depends on your margin, customer lifetime value and what the same money would return in another channel. Always compare against your own channels and periods.
-
Not always. With a long sales cycle, repeat customers or a campaign that has only just started (as with SEO), short-term ROI underestimates the result. Check your time window and attribution before deciding.