Finance · 5 min read
How to Calculate ROI
Net gain over cost — a simple percent return
Return on investment (ROI) is net gain divided by what you spent, as a percent. This tutorial walks through (Final − Cost) / Cost × 100, a $1,000 / $1,350 worked example, and a playground that stacks gain against cost as the live percent updates. Figures are illustrative; fees and taxes are omitted.
Written by the My Calculator Stack editorial team. About our methods
These figures are illustrative. Fees, taxes, and product-specific rules are omitted. This is not investment, tax, or financial advice.
1.What ROI is
ROI asks how much you gained (or lost) relative to the money you put in. A 35% ROI means you earned 35 cents of net gain per dollar of cost. The same identity works for a loss: if the final value is below cost, ROI is negative. This page uses a single cost and a single final value — no holding period, no annualization, and no fees.
2.The formula
ROI = (Final − Cost) / Cost × 100. Cost is the amount invested (the denominator) and must be nonzero. Final is the ending value of that outlay. The numerator is net gain; dividing by cost turns dollars into a percent of capital. The ROI calculator on this site uses the same identity and reports the result with a percent suffix.
\[ \mathrm{ROI} = \frac{\text{Final} - \text{Cost}}{\text{Cost}} \times 100 \]
3.Worked example
Take an initial cost of $1,000 and a final value of $1,350 — the same defaults as the ROI calculator. Net gain is 1350 − 1000 = $350. Then ROI = 350 / 1000 × 100 = 35%. If the position had closed at $800 instead, gain would be −$200 and ROI would be −20%.
\[ \mathrm{ROI}=\frac{1350-1000}{1000}\times 100=35\% \]
4.Gain versus cost
Move cost and final value to see net gain and the live ROI percent update. The bar stacks cost and gain on one dollar scale so the percent is visible as a length, not only as a number. This is a teaching widget — no holding period, no fees, no full calculator chrome. Open the ROI calculator when you want the standalone tool.
Inline playground
Illustrative — fees and taxes omitted
ROI
35.00%
Gain $350.00 · cost $1,000.00
(1350 − 1000) / 1000 × 100 = 35%
Illustrative only — a single cost and a single final value, no holding period, no fees or taxes.
Open the full ROI calculator →5.Open the full calculator
The ROI calculator uses the same (Final − Cost) / Cost identity, the same $1,000 / $1,350 example, and the same limitation that taxes and fees are omitted. Browse other finance tools if you need CAGR, compound interest, or a holding-period rate next.
Try it yourself
Open the related calculator and put these formulas to work.