About the Compound Interest Calculator
See how your money grows with compound interest. Pick the compounding frequency and optionally add a fixed amount every month.
How to use
- Enter principal, rate and time.
- Choose how often interest compounds.
- Add monthly contributions if you invest regularly.
Formula
A = P × (1 + r/n)^(n·t)
Frequently asked questions
What is the compound interest formula?
A = P × (1 + r/n)^(n × t), where P is the principal, r the annual rate as a decimal, n the compounding periods per year and t the number of years.
Does compounding frequency matter?
Yes, but less than the rate and the time invested. Monthly or daily compounding earns slightly more than yearly at the same rate.
What is the Rule of 72?
Divide 72 by the annual interest rate to estimate how many years it takes to double your money. At 8%, money doubles in about 9 years.