Return on investment measures how much you gained relative to what you put in. Add a time period to also see the annualized return. Everything runs in your browser.
ROI = (final value − amount invested) ÷ amount invested. A $10,000 investment now worth $15,000 has a 50% ROI and a $5,000 gain. ROI alone ignores time, so a 50% return over 1 year is very different from 50% over 10. The annualized ROI fixes that — it's the equivalent steady yearly rate, useful for comparing investments held for different lengths of time.
Compound interest · Rental property ROI · Loan calculator
For comparison only — real returns depend on fees, taxes, and timing of cash flows.