About this calculator
Compound interest is the reason small, regular saving turns into real money over time — you earn interest on your interest. This calculator shows the future value of a starting amount plus optional monthly contributions, and separates how much you put in from how much the interest added.
How it works
Interest is compounded monthly. The starting amount grows by the monthly rate every month, and each monthly contribution is added and then compounds too. The result splits your total into what you contributed and the interest earned on top.
Frequently asked questions
What is compound interest?
It is interest earned on both your original money and the interest already added — which is why savings grow faster over time.
How often is interest compounded here?
Monthly, which matches most savings accounts. Contributions are added each month and compound from then on.
Is this a guaranteed return?
No. It is an estimate based on the fixed rate you enter. Real returns vary and are not guaranteed.
Can I leave the monthly contribution blank?
Yes — set it to zero to see how a single starting amount grows on its own.