Compound Interest Calculator
Calculate how an investment grows over time with compound interest and regular monthly contributions, and see the split between contributions and interest earned.
How to use the Compound Interest Calculator
Enter your initial investment amount.
Enter how much you plan to contribute each month, if any.
Enter the expected annual interest rate and how often it compounds.
Enter the number of years you plan to invest.
The calculator shows your final balance, total contributions and total interest earned, plus a simple growth chart.
Compound Interest Formula
A = P(1 + r/n)^(nt) + monthly contributions compounded each periodWhere P is principal, r is annual rate, n is compounding periods per year, and t is time in years.
Example
- 1.Initial investment: $1,000
- 2.Monthly contribution: $100
- 3.Annual interest rate: 7%, compounded monthly
- 4.Time: 10 years
- 5.Final balance ≈ $18,177, of which ≈ $13,000 is contributions and ≈ $5,177 is interest
Frequently Asked Questions
Frequently asked questions about the Compound Interest Calculator
What compounding frequency should I choose?+
Use the frequency your bank or broker actually applies — commonly monthly or annually. More frequent compounding produces slightly higher returns for the same nominal rate.
Are returns guaranteed?+
No. This calculator assumes a constant interest rate for simplicity. Real investments fluctuate, so treat the result as an illustrative projection, not a guarantee.
Does it account for inflation?+
No, the result is shown in nominal (non-inflation-adjusted) terms. Real purchasing power will be lower after accounting for inflation.