Three simple steps
How to use the Compound Interest Calculator
- 01
Enter your starting balance and optional monthly contribution.
- 02
Choose an estimated annual return and time period.
- 03
Compare your total contributions with the projected growth.
Savings calculator
Compound Interest Calculator
Project the future value of savings or investments with monthly compounding and regular contributions.
Instant calculation Runs in your browser
Assumes monthly compounding and contributions at the end of each month.
Projected balance
€150,436.50Total contributed€82,000.00
Estimated growth€68,436.50
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Worked example
€10,000 plus €300 monthly at 5% for 20 years
CalculationMonthly compounding over 240 periods
ResultAbout €150,436.50 projected balance
The method
How it works
Interest on interest
Each month's estimated return is added to the balance, so later returns are calculated on previous growth as well as contributions.
Regular contributions
Monthly deposits are added at the end of each period and begin compounding from the following month.
Projection, not promise
A constant annual return simplifies real markets, where returns, fees and tax treatment vary over time.
Helpful answers
Frequently asked questions
How often is interest compounded?
This calculator compounds monthly and treats the annual rate as twelve equal monthly rates.
Are contributions made at the beginning or end of the month?
They are added at the end of each month, a conservative convention for regular saving projections.
Does the calculation include tax or fees?
No. Platform fees, fund charges, inflation and tax can materially change the real outcome.