ROI Calculator

The formula

ROI = (amount returned − amount invested) ÷ amount invested × 100

It expresses the gain or loss as a percentage of what you put in, so that investments of different sizes can be compared.

Worked examples

• You invest €2,000 and get back €2,600: profit €600, ROI 30%.
• You invest €5,000 and get back €4,200: loss €800, ROI −16%.
• A marketing campaign costing €1,500 brings in €4,500 of extra gross margin: ROI = (4,500 − 1,500) ÷ 1,500 = 200%.

The missing ingredient: time

A 30% ROI is excellent over one year and modest over ten. To compare investments of different lengths, convert ROI into an annualized return:

Annual return = (1 + ROI)^(1 ÷ years) − 1

30% over 3 years: 1.30^(1/3) − 1 = 9.1% a year. The same 30% over 10 years is only 2.7% a year — below inflation in many periods.

Pitfalls to avoid

• Forgetting costs: include fees, commissions, taxes, maintenance and your own time. A property bought for €200,000 and sold for €240,000 has not made 20% if €15,000 went on notary fees and work.
• Using revenue instead of profit: for a business project, the return should be the extra margin generated, not the sales figure.
• Ignoring risk: two investments with the same expected ROI can have very different chances of losing money.
• Inflation: a nominal 10% gain over a period when prices rose 8% is a real gain of about 2%.

The compound interest calculator projects how an annual return turns into a final amount; the percentage increase calculator gives the same figure as ROI for any two values.

Formulas and content last reviewed: October 2026 · About