What is compound interest?

Compound interest is interest calculated on the initial principal, which also includes all of the accumulated interest from previous periods on a deposit or loan. It is essentially 'interest on interest'.

What compound frequencies can I use?

This calculator supports monthly, quarterly, semi-annually, and annually compounding frequencies to model different types of investment accounts.

Compound Interest Calculator

Calculate compound interest for savings, investments, or loans with compounding frequencies and monthly contribution options.

Compound Savings Widget

Contributions are added at each month-end. Non-monthly compounding uses an equivalent monthly growth rate. Terms must contain whole months, up to 100 years.

Initial Principal

Monthly Contribution

Annual Interest Rate (%)

Duration (Years)

Compounding Frequency

Calculation Result

Enter inputs above and click Calculate to view results.

Related Calculators

Simple Interest Calculator Compare with non-compounding returns.
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About Compound Interest Calculator

The Compound Interest Calculator helps you plan your investments and savings by simulating interest accumulation over time. It models how your initial principal and recurring monthly contributions grow when interest compounds monthly, quarterly, semi-annually, or annually.

Compound Interest Formula:

i = (1 + r/n)^(n/12) - 1; m = 12t; A = P(1+i)^m + PMT[((1+i)^m - 1)/i]

Where A is the total end value, P is the principal, r is the annual rate, n is compound frequency per year, t is years, and PMT is the end-of-month contribution. Here i is the equivalent monthly rate and m is the number of months. At 0% interest, A = P + PMT × m.

Frequently Asked Questions

Worked example

Example: 1,000 at 5% annual compounding for one year, with no monthly contributions, grows to 1,050. At 0%, depositing 100 at each month-end for a year adds exactly 1,200.