Compound Interest Calculator
Growth with compounding and monthly deposits.
■ Deposits ■ Interest
Year-by-year growth
About this tool
Compound Interest Calculator shows how a starting amount grows when interest earns interest. Pick how often interest compounds, add regular monthly deposits and see the future value, total interest and a table for each year.
How to use Compound Interest Calculator
- Enter the starting amount, rate and years.
- Choose the compounding frequency and any monthly contribution.
- Read the future value and yearly table.
Questions people ask
What is the compound interest formula?
A = P × (1 + r/n)^(n × t), where P is the starting amount, r the yearly rate, n the compounding periods per year and t the years. 1,000 at 5% compounded yearly for 10 years is 1,000 × 1.05^10 = 1,628.89.
How are monthly contributions handled?
Each deposit is added at the end of the month and grows at the monthly equivalent of your rate: (1 + r/n)^(n/12) − 1. Without compounding differences this matches FV = PMT × ((1 + i)^m − 1) ÷ i for m months at monthly rate i.
Does compounding more often make a big difference?
Less than people expect. At 5%, yearly compounding gives an effective rate of 5.000%, monthly 5.116% and daily 5.127%. The rate and the time invested matter far more.