Compound Interest Calculator

Project growth from principal, contributions, and compounding.

Reviewed: 2026-07-21

Starting amount

Monthly contributionAnnual return (%)Time horizon (years)Compounding frequency

Estimated future value$106,639.02

$70,000.00contributions$36,639.02estimated interest120months invested

This projection assumes a constant return, excludes taxes and fees, and is not investment advice.

Method and assumptions

Project future value from an initial balance, recurring contributions, expected rate, and time. Compounding adds prior returns to the balance used for later growth. Real investment returns vary and may be reduced by taxes, fees, and market losses.

How to use it

Enter the starting balance and recurring contribution.
Set an expected annual return and time horizon.
Compare total contributions, projected growth, and future value.

When it helps

Planning a long-term savings target
Comparing recurring contribution amounts
Understanding the effect of compounding

How to verify the result

Check input units and reference dates first. For an important decision, compare the result with an official source or original document. A rounded display can differ slightly from the underlying value.

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest applies only to principal. Compound interest also earns returns on earlier returns.

Is the projected return guaranteed?

No. The projection assumes a constant rate and does not guarantee market performance.

When are monthly contributions added?

This calculator assumes contributions are added at the end of each month.

Compound Interest Calculator