Return on investment (ROI) answers a simple question: for every dollar I put in, how much did I get back? It's used for stocks, real estate, marketing campaigns and equipment purchases alike. The formula is easy — the mistakes are subtle.
The basic formula
ROI is (final value − initial cost) ÷ initial cost, expressed as a percentage. Put in $10,000, end up with $15,000, and your gain is $5,000 — a 50% ROI. The ROI calculator does this in one step, including the part most people skip.
The mistake almost everyone makes: ignoring time
A 50% return is fantastic in one year and mediocre over ten. Total ROI says nothing about how long the money was working. That's why you also need the annualized return — the steady yearly rate that would produce the same result. A 50% gain over 10 years is only about 4.1% per year; the same 50% in one year is 50% per year. Always compare investments on an annualized basis.
Worked example: two "equal" investments
Investment A doubles your money in 7 years. Investment B grows 60% in 3 years. A looks bigger (100% vs 60%), but annualized, A returns about 10.4%/year and B about 17%/year — B is clearly better. Without annualizing, you'd pick the wrong one. Plug both into the ROI calculator and the annualized line settles it.
ROI isn't the whole story
ROI ignores risk, effort and what you could have earned elsewhere. A 12% return on a risky venture isn't obviously better than 8% on something safe and passive. And for ongoing, compounding investments, you'll want to model contributions over time — that's what the compound interest calculator is for.
Different flavors of ROI
Real estate uses specialized versions like cap rate and cash-on-cash return, because financing and rental income complicate the simple formula — see the rental property ROI calculator. For long-term goals like a nest egg, the retirement calculator projects growth decades out. Pick the tool that matches the decision you're actually making.
Calculating ROI: the bottom line
Calculate ROI as gain ÷ cost, then always annualize before comparing. The biggest headline number is often not the best investment — the one with the best return per year, for the risk you took, usually is.