Dividing the total by the years ignores that each year compounds on the last
Growing 10,000 to 16,000 is a total return of 60% and a growth multiple of 1.6. Dividing 60 by 5 gives 12%, which is wrong: it assumes each year’s return applies to the original 10,000. The compound rate is the fifth root of 1.6, less one — 9.86%.
Check it forward and the difference is obvious. Five years at 9.86% turns 10,000 into 16,000; five years at 12% turns it into 17,623. The simple average overstates by more the longer the period and the higher the return, which is why every published fund return uses the compound figure.
Volatility is what opens the gap, and it never closes it
A portfolio gaining 50% then losing 50% has an arithmetic average of zero and is down 25% — a compound return of −13.4% a year. The two averages coincide only when every period return is identical; any variation pulls the compound figure below the arithmetic one, and more variation pulls it further.
This is why volatility costs money even when it averages out. A steadier path to the same arithmetic mean ends with more capital, and the size of that drag rises roughly with the square of the volatility. It is the single strongest argument for diversification stated in return terms rather than risk terms.
The formula handles fractions, and rounding them distorts short holdings
The exponent is one over the number of years, and that number need not be an integer. A holding of eighteen months is 1.5, and entering 2 instead understates the annualised return materially. For short periods the effect is large, because the root is taken over a small exponent.
The opposite caution applies to very short periods. Annualising a strong month by raising it to the twelfth power produces a spectacular and meaningless figure — a 5% month is 79.6% annualised, which no one should quote. Annualisation assumes the rate is repeatable, and over short windows it usually is not.
Money added or withdrawn along the way
The calculation compares one starting value against one ending value, which describes a lump sum left alone. The moment money is added or taken out, the figure stops measuring the investment’s performance and starts measuring a mixture of performance and timing.
For a portfolio paid into regularly, XIRR is the correct measure — it weights each cash flow by how long it was invested. Time-weighted return is the other alternative, used by funds precisely because it removes the effect of investor cash flows and measures the manager alone.
Frequently Asked Questions
Can annualized return be negative?
Yes. If the ending value is below the beginning value, the growth multiple is less than one and the annualized return is negative, reflecting an average yearly loss.
Does this account for money I added during the period?
No. This formula assumes a single lump sum held from start to finish. If you made additional contributions or withdrawals, use an XIRR or money-weighted return instead.
What is the difference between annualized and absolute return?
Absolute return is the raw percentage gain over the whole period regardless of time. Annualized return restates that gain as a per-year rate so periods of different lengths can be compared fairly.
Can I use this for comparing two funds?
Yes, as long as both figures cover the same kind of measurement (lump sum, same fees treatment). The annualized rate is exactly the metric used to line up investments held for different lengths of time.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Returns are assumptions, not guarantees. Actual results may vary because of market performance, taxes, fees, inflation, and timing. This is an educational projection, not investment advice.
Published the calculator with its formula, worked example, assumptions, limitations and a bespoke guide, and added an automated formula test suite covering it.
Verified the compound rate against the growth multiple it implies, and confirmed it never exceeds the total return divided by the years — the error this page exists to correct.
Frequently Asked Questions now show on the page: 4 answers, checked in a page-by-page audit.
Add this calculator to your site
Responsive embed — and private: nothing your visitors type leaves their browser.