ROI answers “compared to what?”
“I made $250” is only half a sentence. Made $250 from what? ROI finishes it by dividing the gain by the amount you committed to get it. A $250 gain on $1,000 is a return of 25%. The same $250 on $5,000 is a return of 5%.
The formula
Subtract what you put in from what you got back, then divide by what you put in:
ROI % = (amount returned − amount invested) / amount invested × 100
Put $1,000 in and get $1,250 back: (1,250 − 1,000) / 1,000 × 100 = 25%.
Same gain, different ROI
Hold the profit at $250 and change only the stake. The ROI falls away as the amount invested grows, because the gain is being measured against a bigger number:
| Invested | Returned | Gain | ROI |
|---|---|---|---|
| $1,000 | $1,250 | $250 | 25% |
| $2,500 | $2,750 | $250 | 10% |
| $5,000 | $5,250 | $250 | 5% |
| $25,000 | $25,250 | $250 | 1% |
A loss is a negative ROI
If you get back less than you put in, the gain is negative and so is the ROI. Getting $1,600 back on $2,000 is a −400 / 2,000 × 100 = −20% ROI. Losing the whole stake is −100%.
What ROI leaves out
ROI is one ratio. On its own it does not capture:
- Time. A 25% ROI earned over one year and a 25% ROI earned over ten years are both “25% ROI.” To compare returns of different lengths you need an annualized ROI, which spreads the return across the number of years.
- Risk. ROI describes what happened (or a projection); it says nothing about how likely that outcome was.
- What the numbers include. “Amount invested” should include fees and costs; “amount returned” should include any income received along the way, not just the final resale value. Define both consistently or the ratio is not meaningful.
ROI is not profit margin
Both are a profit divided by something, but the denominators are different questions. Profit margin divides profit by revenue — the slice of a sale you keep. ROI divides the gain by the amount invested — how hard your committed money worked. A business can have a healthy margin on each sale and a poor ROI on the capital behind it, or the reverse.
Common mix-ups
- Quoting the dollar gain as “the return.” “A $10,000 return” means nothing without the amount invested next to it.
- Comparing ROIs over different time spans. A 30% ROI over three years is worse than a 15% ROI over one year, even though 30 > 15.
- Leaving costs out of the amount invested. Fees, commissions and improvement costs are part of what you put in; omitting them inflates the ROI.
- Treating a projected ROI as a fact. An expected return is an estimate, not an outcome.
Frequently asked questions
What counts as a good ROI?
It depends on the risk taken and how long the money was committed — ROI on its own captures neither. A higher ROI is only better when the risk and the time frame are comparable. PercentFox does the arithmetic; it does not give investment advice.
Does ROI take time into account?
No. A 25% ROI over one year and over five years are the same ROI. To compare returns over different periods, annualize them by spreading the return across the number of years.
Can ROI be more than 100%?
Yes. An ROI above 100% means you got back more than twice what you put in. Turning $1,000 into $2,500 is a 150% ROI.
Is ROI the same as profit margin?
No. Profit margin is profit as a percent of revenue. ROI is the gain as a percent of the amount invested. They use different denominators and usually give different numbers.