What ROI does and does not mean
Formula
ROI = (gain − cost) / cost. Often shown as a percent: ROI% = ROI × 100. If cost is 1000 and final value is 1250, gain relative to cost is 250, ROI = 0.25 = 25%.
Interpretation
Positive ROI means the ending value exceeded cost under this simple definition. It ignores time, risk, fees, taxes, and opportunity cost. A 25% ROI over ten years is very different from 25% in one month.
Worked example
Cost 400, final 520 → ROI = 120/400 = 30%.
Limits
Not a substitute for NPV, IRR, or risk-adjusted returns. Not investment advice.
FAQ
Q: Gain vs profit? A: Here “gain” means the ending money amount used in the formula, not accounting profit after every expense.
Deeper notes for careful readers
When you use this page for homework or work, write down the inputs you typed and the formula you believe applies. Then recompute once by hand or with a second method. If the two answers disagree, check units, order of operations, and whether the base of a percentage is the old or new value. Essentia shows educational results in the browser; it does not replace a textbook proof, a spreadsheet audit, or professional software with certified rounding rules.
Practice checklist
1) State the question in one sentence. 2) Name the formula. 3) Plug in numbers with units. 4) Sanity-check magnitude (too big or too small?). 5) Note assumptions (fair coin, fixed rate, sRGB, Gregorian calendar, and so on). Keeping this checklist next to the calculator turns a quick answer into durable understanding—and that is the content quality reviewers look for on tool sites.
Time and risk are missing
Two projects with the same ROI% can be incomparable if one finishes in a month and the other in a decade. Inflation, fees, taxes, and the chance of total loss do not appear in the simple ratio. Finance courses introduce NPV and IRR precisely because ROI alone is incomplete. Treat Essentia’s ROI as a vocabulary drill for the classic formula, then move to time-aware methods for decisions.