ROI: why percent return beats dollar profit
ROI answers a simple question: for every dollar put in, how much came back? It's one formula, but it does something a raw dollar-profit figure can't — it lets you compare a $10,000 bet against a $3,000 one on equal footing.
The formula
ROI = (final value − cost) ÷ cost × 100. Profit is just the final value minus the cost; ROI turns that dollar figure into a percentage of what it took to get there.
A real example: two deals, compared
Deal A: put in $10,000, it's now worth $11,800.
- Profit:
11,800 − 10,000 = $1,800. - ROI:
1,800 ÷ 10,000 × 100 = 18%.
Deal B: put in $3,000, it's now worth $3,800.
- Profit:
3,800 − 3,000 = $800. - ROI:
800 ÷ 3,000 × 100 ≈ 26.67%.
Deal A made more actual money — $1,800 versus $800. But Deal B was the better use of the dollars put in: every dollar in Deal B returned about 26.7 cents of profit, versus 18 cents for every dollar in Deal A. Which one is "better" depends on whether you're optimizing for total dollars or for how hard each dollar worked — and if the $7,000 difference in size could have gone into more of Deal B, ROI is the number that tells you that was on the table.
A real example: a loss
The same formula works in reverse. Put $5,000 into an investment that's later worth $3,200.
- Profit:
3,200 − 5,000 = −$1,800. - ROI:
−1,800 ÷ 5,000 × 100 = −36%.
A −36% ROI means just over a third of the original money is gone. Framing a loss as a percentage rather than only a dollar figure makes it comparable to other losses (or gains) of a completely different size — a $1,800 loss on a $5,000 bet is a much bigger deal, proportionally, than the same $1,800 loss on a $50,000 one.
Why percent beats a raw dollar figure
Dollar profit tells you the outcome of one specific bet. ROI tells you how efficiently the money was used, which is the number that actually transfers to the next decision: if you have $10,000 to invest and two options with different ROIs, the percentage — not the dollar profit of whatever you happened to try last time — is what should drive where the next dollar goes.
What this doesn't capture
ROI is a total return over whatever period the money was invested — it says nothing about how long that took. An 18% ROI over one year and an 18% ROI over five years are very different outcomes, but the formula above treats them identically. For a return that accounts for time, use CAGR instead, which spreads the same total gain across the actual number of years it took.
Run your own numbers
The free ROI calculator runs this instantly for your own numbers — entirely on your device.