What is the ROI Calculator?
Return on investment expresses gain relative to cost as a percentage, which allows very different opportunities to be compared on one scale. Its simplicity is both its strength and its principal limitation.
This calculator computes ROI from an initial cost and a final value. The number it gives says nothing about how long the return took, which is why it should rarely be used alone.
What each input means
- Current or final value
- What the investment is now worth or what it returned in total.
- Initial cost
- The full amount invested, including any associated costs of making the investment.
How this calculation works
The calculation subtracts cost from final value and divides by cost, expressed as a percentage. A hundred invested returning a hundred and thirty produces a thirty percent return.
The missing dimension is time. Thirty percent over one year and thirty percent over ten are the same ROI and vastly different outcomes. Where duration differs between options, an annualised measure such as CAGR is the appropriate comparison.
Formula: Result = the relevant inputs combined using the displayed assumptions.
Getting the most out of the result
- Always pair ROI with the time period. Without it the figure is close to meaningless for comparison.
- Include every cost of the investment — fees, taxes, and the time you spent if it was substantial.
- Use annualised return when comparing investments held for different lengths of time.
- Consider risk alongside return. A high ROI achieved by taking large risks is not straightforwardly better.
- For marketing spend, be careful about attribution. Revenue that would have arrived anyway is not return on the campaign.
Common mistakes to avoid
The dominant error is comparing ROI figures from investments held over different periods, which makes a slow-performing option look equal to a fast one. Costs are also routinely understated — transaction fees, taxes and the owner's own time rarely appear in the denominator. In marketing, attributing all resulting revenue to a campaign ignores what would have happened without it. And ROI is regularly quoted without any reference to the risk taken to achieve it.
Frequently asked questions
What is a good ROI?
It depends entirely on the time period, the risk and the alternatives available. Twenty percent over five years is unremarkable; twenty percent over three months is exceptional. Always ask over what period and at what risk.
How does ROI differ from CAGR?
ROI is total return over the whole period, ignoring duration. CAGR expresses that return as a constant annual rate. For comparing investments held over different lengths of time, CAGR is the appropriate measure.
Should time be included in the cost?
If the investment demanded significant personal effort, yes — otherwise you overstate returns on labour-intensive activity relative to passive alternatives. Value it at what your time could otherwise have earned.
Can ROI be negative?
Yes. When the final value is below what you put in, the return is negative, expressing the share of your original investment that has been lost rather than gained. A negative ROI is not the same as losing everything — a minus 30 percent ROI means you still hold two-thirds of your capital, not none of it. The figure worth remembering is that losses and gains are not symmetric: a 50 percent loss requires a 100 percent gain just to get back to where you started, because the recovery has to happen on a smaller base than the one you lost from. This is why avoiding a large loss matters more than chasing an equivalent gain, and why an ROI figure is worth reading for what it actually implies rather than just checking whether the sign is positive or negative.
How do I calculate ROI on marketing?
Divide the profit attributable to the campaign, not the revenue, by the campaign cost. Attribution is the hard part — isolate incremental results rather than crediting the campaign with sales that would have occurred anyway.
Does ROI account for risk?
No, and that is its main weakness. Two investments with identical ROI can carry entirely different probabilities of loss. Consider return and risk together rather than ranking on return alone.
Should ROI be calculated before or after tax?
After tax gives the more realistic picture of what you actually keep, particularly when comparing investments with different tax treatments. Be consistent across every option you compare.