Return on investment
181.3%
- Net gain or loss
- $1,160
- Total cost
- $640
- Total benefit
- $1,800
- Monthly net after running costs
- $130.00
- Payback of the upfront cost
- 4 months
- Annualised return
- 181%
- Only meaningful if the same monthly result would really continue.
This calculator produces estimates from the numbers you enter, so it is only as accurate as your inputs. It is not tax, accounting or legal advice. Rules and fees differ by country and change over time; check the current terms that apply to you.
The short answer
Return on investment is your net gain divided by what you spent. Add the upfront cost to the ongoing costs over the period, compare it with the extra income the purchase really produces, and divide the difference by the cost. The hardest part is honesty: count only the income the purchase caused, and every cost, including subscriptions.
Worked example
These are the example values loaded into the calculator above, run through exactly the same formulas, so you can check the method against your own numbers.
| Inputs | |
|---|---|
| Upfront cost | $400.00 |
| Ongoing monthly cost | $20.00 |
| Extra income per month | $150.00 |
| Period | 12 months |
| Results | |
|---|---|
| Total cost | $640.00 |
| Total benefit | $1,800 |
| Net gain | $1,160 |
| Return on investment | 181.3% |
| Payback of the upfront cost | 4 months |
Every online business runs on small purchases: a course, a subscription, a piece of equipment, a month of advertising. Each looks reasonable alone. Together they can quietly cost more than they return. Return on investment is the simple test that keeps score, and this calculator applies it to a purchase with both upfront and ongoing costs.
How to use this calculator
- Enter the upfront cost: the course fee, equipment price or campaign set-up.
- Enter any ongoing monthly cost, such as a subscription or advertising spend.
- Enter the extra income or savings per month the purchase produces.
- Choose the period you want to judge it over.
the numbers on the page are example values. The result is only as reliable as the benefit you enter, so be strict about what really counts.
The formulas
- Total cost = upfront cost + (monthly cost × months)
- Total benefit = monthly benefit × months
- Net gain = total benefit − total cost
- ROI = net gain ÷ total cost
- Payback time = upfront cost ÷ (monthly benefit − monthly cost)
- Annualised ROI = (1 + ROI) ^ (12 ÷ months) − 1
For the default example, the total cost is 640, the benefit is 1,800, the gain is 1,160 and the ROI is 181.25%. The calculator is tested against hand-worked cases, including the property that a twelve-month result annualises to itself.
The honest-benefit problem
The formula is trivial. The hard part is the benefit figure. It should contain only the income or savings the purchase genuinely caused. If you bought a course and your income rose, ask what else changed: more hours, a new client, a seasonal boost. Credit the purchase only for what you can trace to it. If you cannot show where the gain came from, use a lower figure, or zero.
The same discipline applies to costs. Include subscriptions you forgot to cancel, the time you spent (see the effective hourly rate calculator), and any fees. A purchase that only looks profitable when costs are left out is not profitable.
Payback time
Payback answers a practical question: how long until I have my money back? A short payback means less exposure. A long one, or none, means you are relying on the purchase continuing to work far into the future. For small businesses, where cash matters, a slow payback can be a problem even when the eventual ROI looks healthy.
Why be careful with annualised figures
Annualising takes a short-period result and projects it across a year. It is useful for comparing options measured over the same time. It is dangerous as a forecast, because early results often do not persist. If you see an annualised ROI in the thousands of percent, treat it as a sign that the period is too short to conclude anything.
Using ROI to avoid bad purchases
Numbers cut through sales pages. Before buying a course or programme that promises a large return, ask what it would need to produce to pay for itself, and whether you have any evidence it could. Be extra sceptical of anything that guarantees a return; our online income scam checker covers the warning signs, and our comparison of free versus paid ways to make money online explains when spending money is worth it. For advertising specifically, use the break-even ROAS calculator, and for the tools themselves see our guide to online business tools.
Common mistakes
Counting hoped-for income. Only count what you can trace.
Leaving out ongoing costs. Subscriptions add up.
Ignoring your time. It is a real cost.
Judging over too short a period. A month can mislead in either direction.
Falling for sunk costs. What you already spent is gone. Judge whether to keep spending by what happens next.
Assumptions and limits
The calculator assumes constant monthly costs and benefits, ignores tax and the time value of money, and treats the benefit you enter as certain. Real returns vary and can be negative. It is a discipline for judging decisions, not a prediction, and it is general information, not financial advice.
Frequently asked questions
How do you calculate ROI?
Subtract total cost from total benefit to get the net gain, then divide by the total cost and multiply by 100. If a purchase costs 640 in total and produces 1,800 of extra income, the net gain is 1,160 and the ROI is 181%. Include ongoing costs, not only the upfront price.
What is payback time?
It is how long the monthly net benefit takes to repay the upfront cost. If a tool costs 400 upfront and adds 130 a month after its running costs, it pays back in about three months. If the monthly benefit does not exceed the monthly cost, it never pays back.
Why is annualised ROI misleading for short periods?
Annualising assumes the same result would repeat for a full year, compounding as it goes. A great first month can produce an enormous annualised figure that reality never delivers. Treat it as a way to compare options over the same period, not as a forecast.
How do I know how much income a purchase really caused?
It is often hard. Compare what you earned before and after, allow for other things that changed, and be sceptical of gains you cannot trace. If you cannot say where the extra income came from, count only what you can evidence.
How we keep this calculator accurate
The formulas on this page are standard arithmetic, written out in full above so you can check them. Each one is covered by automated tests that compare the calculator against independently worked examples and round-trip checks, and the worked example is generated by the same code as the calculator. We use no third-party data, exchange rates or fee tables, because those go stale; fees and rates are always numbers you enter. If you spot a mistake or an assumption that does not fit your situation, please tell us. Our earnings disclaimer and editorial approach explain how the site works.
Written by
The editorial team behind How To Make Money Online, responsible for researching, writing, and fact-checking every guide on this site against current platform terms and fees.