Key takeaways
- ROI = ((Final Value − Initial Cost) ÷ Initial Cost) × 100.
- ROI is always measured against the initial cost, never the final value.
- A positive ROI means a gain; a negative ROI means a loss.
- Plain ROI ignores how long the investment took — that's what CAGR is for.
In this guide
What is ROI?
ROI, or return on investment, measures how efficient an investment was: how much you gained relative to how much you put in. A higher ROI means you got more profit for every dollar invested, which makes it useful for comparing choices like stocks, a small business, or even a home renovation.
Why does ROI matter?
Raw profit numbers can be misleading on their own. ROI strips away the size of the investment and shows the percentage return, so a $500 gain on a $1,000 investment and a $500 gain on $10,000 clearly don't perform the same.
Invest $5,000 in a small side business and grow it to $6,500 in a year, and your ROI is 50%, even though the dollar gain is only $1,500.
The formula
| Symbol | What it means | Example |
|---|---|---|
| Final Value | What the investment is worth now | $6,500 |
| Initial Cost | What you originally spent | $5,000 |
| ROI | The return as a percentage of cost | 30% |
How to calculate ROI step by step
- 1Subtract the initial cost from the final value. This gives the profit (or loss).
- 2Divide that profit by the initial cost. This puts the result on the same scale, regardless of size.
- 3Multiply by 100. This turns the result into a percentage.
- 4Read the sign. Positive ROI is a gain, negative ROI is a loss.
Enter your own investment numbers in the calculator below to see each step.
Try it yourself
Pre-filled with the example — change any value.
Common mistakes to avoid
- Forgetting to include all costs. If fees, taxes, or upkeep were part of the investment, they should be added to the initial cost for an accurate ROI.
- Comparing ROI without matching time periods. A 20% ROI in one year is very different from a 20% ROI over ten years — plain ROI alone doesn't account for time.
- Treating ROI as a guarantee. ROI describes what already happened, not what will happen next.
Tips and tricks
- To account for how many years an investment took, use the CAGR calculator, which turns a total return into an annual growth rate.
- For measuring returns on individual product sales rather than a whole investment, the profit margin calculator is a closer fit.
- Comparing several options? List them side by side with their ROI and time period together, not ROI alone.
Where you'll use it in real life
- Investing: comparing stocks, funds, or property purchases against how much was put in.
- Marketing spend: businesses measure ROI on ad campaigns by comparing revenue generated to money spent.
- Small business decisions: evaluating whether a new piece of equipment or a renovation paid off.
- Personal finance: checking whether a side project or resale venture was actually worth the time and money.
Quick summary
ROI is ((Final Value − Initial Cost) ÷ Initial Cost) × 100 — find the profit, divide by what you spent, then multiply by 100. It's a fast way to compare gains of very different sizes fairly. Use the calculator above to check your own investment's ROI.
Worked example
You invested $5,000 in a small side business, and after a year of sales, your stake is now worth $6,500.
- 01ROI = ((Final Value - Cost) / Cost) × 100
- 02Profit = $6,500 - $5,000 = $1,500
- 03ROI = (1500 / 5000) × 100
- 04ROI = 30%
These numbers are pre-filled in the calculator above.
Frequently asked questions
What counts as a good ROI?
It depends heavily on the type of investment and time period involved, so there's no single "good" number — comparing ROI against similar investments over the same time frame is more useful than judging it in isolation.
How is ROI different from profit?
Profit is a raw amount of money (final value minus cost). ROI turns that profit into a percentage of the initial cost, which makes it possible to compare investments of very different sizes.
Does ROI account for how long the investment took?
No, plain ROI does not factor in time. Two investments with the same ROI but different durations had very different rates of return — for that, use the CAGR calculator instead.
Can ROI be negative?
Yes. If the final value is less than the initial cost, the profit is negative, and so is the ROI — meaning the investment lost money.
