Compound Interest Calculator

How to use it

1. Enter your starting savings, annual rate, years and recurring contribution.
2. Choose compounding and contribution frequencies in advanced options.
3. Review final balance, total contributions and the year-by-year breakdown.

The method

The nominal annual rate is converted to an effective rate per contribution interval using (1 + rate/compounds)^(compounds/frequency) − 1. Contributions are added at the chosen start or end of each interval.

For example

With 1,000 initially, 100 each month and a 0% rate, the balance after one year is 2,200.

The rate stays constant. Taxes, fees, inflation and market volatility are not included. Growth is a mathematical projection.

Using Compound Interest Calculator with the right inputs

Project savings growth with recurring contributions. Start by matching your task to the quantities and options shown below. The definitions of the inputs matter as much as the final number or transformed output; retain the original values so that you can repeat or check the result.

Inputs and options explained

• Starting amount: Enter the numeric value for this quantity using the units or scale shown in the label. The form indicates a minimum of 0.
• Annual interest rate (%): Enter the percentage in the scale shown by the label; for a field marked %, enter 5 for five percent rather than 0.05. The form indicates a minimum of 0.
• Years: Enter the numeric value for this quantity using the units or scale shown in the label. The form indicates a minimum of 1 and a maximum of 100.
• Regular contribution: Enter the numeric value for this quantity using the units or scale shown in the label. The form indicates a minimum of 0.
• Compounding frequency: choose Monthly, Annually, Quarterly, Daily (365 days).
• Contribution frequency: choose Monthly, Annually, Weekly (52 per year).
• Contribution timing: choose End of period, Beginning of period.

Method and interpretation

The calculation combines growth on the current balance with recurring contributions. The annual rate, compounding frequency and contribution interval determine the effective rate used for each contribution period. Contributions made at the start of a period grow for longer than contributions made at its end.

Worked example

Start with 1,000, add 100 each month for one year and set the interest rate to 0%. The closing balance is 1,000 + 12 × 100 = 2,200. Adding a positive rate then isolates the effect of growth from the money you contributed.

Assumptions and limitations

The entered rate remains constant in this model. Taxes, fees, inflation, withdrawals and changing market returns can materially alter real outcomes. A projected balance is not a promised return; compare several rate assumptions and separate contributions from growth when reading the result.

Before you use the output

• Choose the intended action: Project savings. Re-run the operation after changing an input or mode so that you are checking the updated result.
• Read the result label and any accompanying explanation. Keep the input values or source file with the output so that a later comparison uses the same assumptions.
• If a result looks unexpected, check units, separators and selected options first. Try a smaller example you can verify rather than repeatedly changing several settings at once.

Questions or a result that needs checking?

If you find a discrepancy, report a problem with Compound Interest Calculator. Include a non-sensitive example, the selected options, the result you expected and the result shown. This makes the issue easier to reproduce. See About & privacy for how the site handles tool inputs.