Compound Interest Calculator
What you get
The final amount and the interest, together
Enter a principal, a rate and a number of years and get both figures at once — what the sum grows to, and how much of that is interest.
Compounded once a year
The rate is applied once per year unless you are told otherwise. Compounding monthly or daily gives a different, usually larger, number.
No currency imposed
The numbers are currency-neutral — the answer works the same way whatever currency the sum is in.
Nothing is stored
Your principal, rate and years stay on your page. We do not store them or send them anywhere.
How it works
- Enter the principal.
- Enter the annual rate, as a percentage.
- Enter the number of years, and get the final amount and the interest earned.
Worth knowing
What the calculation does
Compound interest means the annual rate is applied to a sum that already includes every earlier year's growth, not to the original principal alone — the amount is multiplied by (1 + rate) once for every year, so the growth itself starts earning too. At a rate of zero nothing grows: the final amount is the principal, and the interest is zero.
What it leaves out
The figure assumes the rate holds for the whole period, ignores tax on the interest, and ignores inflation — a sum that grows at the same rate prices rise has bought nothing. It also assumes yearly compounding: compounding monthly gives a different, slightly larger, number.
Frequently asked questions
Why does no currency appear?
Because the arithmetic is the same regardless of currency — the answer works the same way whatever currency the sum is in.
Is this figure guaranteed?
No. It assumes the rate holds for the whole period, which no real deposit or investment guarantees, and it is not financial advice.
Does it account for tax or inflation?
No. Tax on the interest and the effect of inflation are both left out, and both reduce what the growth is actually worth.
What if the interest compounds monthly instead of yearly?
This works out yearly compounding. Compounding monthly applies the rate twelve times a year instead of once, which gives a different, usually larger, final amount.