About the ROI Calculator
ROI is the most quoted investment figure and the most misused, for one reason: it has no time in it at all.
"A 40% return" is not something you can act on. Over one year it is excellent. Over eight years it is 4.3% a year, which is worse than a savings account. The number is identical in both cases.
That is not a subtlety. It is the single most important thing to know about ROI, and it is why this calculator reports the annualised figure as the headline and treats the plain ROI as the less useful of the two.
It also insists on two things most ROI calculations skip: that costs are part of what the investment cost you, and that borrowing makes "ROI" mean two different numbers.
How to Use the ROI Calculator
Amount invested and costs on top together make the outlay. Costs means fees, taxes, stamp duty, renovation, holding costs, selling costs — everything.
Amount returned and income received together make the proceeds. Income is rent, dividends or interest collected along the way.
Of which borrowed — leave at zero if none of it was. If some was, the calculator separates the return on the deal from the return on your cash.
Held for is the one people skip, and without it there is no annualised figure and nothing to compare.
Step-by-Step Example
A property: £200,000 paid, £15,000 of costs, sold for £260,000, £24,000 of rent collected, £150,000 of it borrowed, held five years.
Outlay: 200,000 + 15,000 = 215,000.00
Proceeds: 260,000 + 24,000 = 284,000.00
Gain: 69,000.00
ROI: 69,000 / 215,000 = 32.09%
Annualised: (1.3209)^(1/5) − 1 = 5.72% a year32.09% is the number that gets quoted. 5.72% a year is the number that tells you whether it was any good — and against a decent savings account over the same five years, it is not obviously a triumph.
Costs Belong in the Denominator
Drop the £15,000 of costs and the ROI rises to 42% — 5.72% a year becomes 7.26%. Nothing about the investment changed; only what you counted. Note that leaving costs out moves the figure twice: it lowers the outlay and raises the gain, because the gain is proceeds minus outlay.
This is the most common way an ROI gets overstated, and on property it is routine. Purchase price is not what something cost you. Stamp duty, legal fees, survey, renovation, agent's commission, mortgage arrangement fees, insurance and maintenance while you held it — all of it is money you put in and cannot spend elsewhere.
If an ROI is quoted without saying what was in the denominator, assume it is flattering.
The Two Different Numbers Called ROI
Borrowing splits the answer, and both halves are legitimately called ROI.
Return on the outlay: 69,000 / 215,000 = 32.09%
Your own cash in: 215,000 − 150,000 = 65,000
Back to you: 284,000 − 150,000 = 134,000
Return on your cash: 69,000 / 65,000 = 106.15%106.15% against 32.09%, on the identical deal.
Borrowing did not improve the investment. It concentrated the same result onto less of your cash. The property performed exactly as it performed; the leverage changed only how much of the outcome landed on your share.
And it does the same thing to losses. If that property had sold for £100,000, the loss falls on your £65,000 first — the lender is repaid in full regardless.
Anyone quoting an ROI on a leveraged deal is almost always quoting the second number without saying so. Both are true; only one of them is the return on the investment.
Recovering From a Loss
Losses are asymmetric, because the gain needed is measured against a smaller base:
A 40% fall: 10,000 → 6,000
To recover: 6,000 → 10,000 = a 66.67% gain| Loss | Gain needed to recover |
|---|---|
| 10% | 11.1% |
| 25% | 33.3% |
| 40% | 66.7% |
| 50% | 100% |
| 75% | 300% |
This is why avoiding large losses matters more than catching large gains, and why leverage cuts much harder on the way down than it flatters on the way up.
Understanding Your Result
Return leads with the annualised figure, because that is the comparable one.
Total return is the plain ROI with the gain and the outlay it came from.
Annualised shows the conversion explicitly — or, if you left the period out, explains why there is no answer.
On your own cash separates leverage from performance.
Worth knowing is the caveat that applies: the recovery arithmetic on a loss, or a warning that a respectable-looking total is a poor annual rate.
When Should You Use This Calculator?
Before comparing two investments. Annualise both or you are not comparing anything.
On any property deal. Costs and leverage both matter enormously here.
When you are shown an ROI. Ask what period it covers and what was in the denominator. If the answer is vague, that is the answer.
After selling something. Working out what you actually made, including everything it cost to own.
Common Mistakes
Comparing ROIs across different holding periods. They are not comparable. This is the big one.
Leaving costs out. Inflates the return and is very easy to do accidentally.
Quoting the leveraged return as the investment return. Both are real; they answer different questions.
Forgetting income. Rent and dividends are part of the return, and leaving them out understates a yielding asset badly.
Assuming a loss recovers at the same percentage. A 50% fall needs a 100% gain.
Ignoring inflation. A 5.72% nominal annual return against 3% inflation is a real 2.64%.
Confusing ROI with CAGR. ROI is a total; CAGR is annualised. The interest rate calculator does the same job from a start value, an end value and a period.
Every figure here is an estimate for planning, not financial advice.