Starting amount, annual return and years → what you'd end up with, compounded monthly.
Year-by-year progression
| Year | Monthly contribution | Contributed | Interest | Balance |
|---|
Assumes interest compounds monthly, contributions are added at the end of each month, and (if set) your monthly contribution increases once per year by the percentage entered above.
About this calculator
Compound interest is calculated as Principal × (1 + rate÷12)^months for the initial amount, plus the future value of any monthly contributions added along the way.
Because interest is calculated on interest already earned, growth accelerates over time — the longer the time horizon, the bigger the gap between compound and simple interest.
The annual contribution increase models a rising monthly payment — for example, if you expect to put away 2% more each year as your income grows. Every 12 months, the monthly contribution used in the calculation goes up by that percentage.
The currency selector only changes the symbol shown next to your results — it doesn't convert between currencies, so make sure all your inputs are already in the currency you pick.
Frequently asked questions
How much difference does compounding monthly rather than annually make?
A modest but real one. More frequent compounding means interest starts earning its own interest sooner, so the same headline rate grows slightly faster — the gap widens the longer you leave it invested.
Why does the growth accelerate later on?
Because interest is paid on interest already earned. Early on there is little accumulated interest to compound, but after a decade or two the returns generated by past returns can dwarf your own contributions.
Does the annual contribution increase compound too?
Yes. Each year your monthly contribution rises by the percentage you set, and every one of those larger contributions then earns returns for the remaining time — so a small yearly increase adds up substantially.