Compound Interest Calculator
Compound interest calculator with monthly contributions. See the future value of your savings, total contributed and interest earned over any period.
Formula
FV = P(1 + r/n)^(nt) plus the future value of monthly contributions.
Use it from the API
curl "https://moltcalc.com/api/calc/compound-interest?principal=10000&rate=8&years=10&frequency=12&contribution=200"
See the API docs for every endpoint and the input schema.
FAQ
How does compound interest work?+
You earn interest not just on your original deposit but also on the interest already earned. The calculator uses FV = P(1 + r/n)^(nt), where n is how many times per year interest compounds and t is the number of years.
Does compounding frequency matter?+
Yes, but less than people expect. Daily compounding earns slightly more than monthly, which earns slightly more than annual, at the same stated rate. The interest rate and time invested matter far more.
How are monthly contributions counted?+
Contributions are treated as a monthly deposit stream that compounds at the monthly rate, so earlier deposits have more time to grow. Their future value is added to the growth of your starting amount.