Compound Interest Calculator
Estimate how a starting amount and repeated monthly contributions could grow at a constant annual rate. The result separates your deposits from calculated interest.
iMonthly compounding; contributions are added at the end of each month.
Use it without guessing.
- 01Enter a starting balance and monthly contribution.
- 02Set an annual rate and time horizon.
- 03Compare total contributions with the projected ending balance.
What the number means
This model compounds monthly and assumes contributions are made at the end of each month. It uses a constant rate and does not model volatility, taxes, fees or inflation.
The output is a mathematical scenario, not a forecast or investment recommendation. Real returns vary and can be negative.
Before you rely on the output
What compounding frequency does this use?+
Monthly compounding with contributions added at the end of each month.
Is the annual rate guaranteed?+
No. It is an assumption for the calculation. Market, savings and lending rates can change.
Why is the result different from my bank?+
A bank may compound daily, apply tiered rates, round differently, charge fees or calculate contributions on different dates.