Compound Interest Calculator
Enter a principal, annual rate, term and compounding frequency — plus optional monthly contributions — to project your final balance, total contributions and total interest earned, with the formula shown.
Examples
$1,000 · 5% · 10 yr · monthly
≈ $1,647 balance · $647 interest
How it works
The starting amount grows by A = P × (1 + r ÷ n)^(n × t), where r is the annual rate, n is how many times a year interest is added and t is the number of years. Monthly contributions are treated as paid in at the end of each month and grow at the matching monthly rate.
| Compounding | Final balance |
|---|---|
| Annually | 1,628.89 |
| Quarterly | 1,643.62 |
| Monthly | 1,647.01 |
| Daily | 1,648.66 |
More frequent compounding helps, but only a little; time and the rate matter far more. The projection assumes the rate never changes and leaves out tax, fees and inflation, so read it as an estimate, not a forecast.
How to use Compound Interest Calculator
Why use this tool
Frequently asked questions
A = P(1 + r/n)^(nt) for the principal, plus the future value of regular monthly contributions compounded at the matching rate.
Each monthly deposit earns interest from the month it's added until the end of the term, using a monthly rate derived from your compounding frequency.
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