Monthly compounding
The effective annual rate is converted to an equivalent monthly rate. The balance is updated at that rate every month.
A calculation that needs no external data
Compound Interest Calculator: See the Effect of Regular Contributions
Enter your starting amount, monthly contribution, and own rate assumption. Review the amount you contribute and the calculated compounding effect separately over time.
MetriLume does not suggest a rate; the calculation uses only the assumption you enter.
Calculator
Build your own scenario.
Fields are used only for the calculation on this screen. They are not written to the URL, analytics, or device storage.
Method
How the result is calculated is clear.
Contribution timing
A start-of-month contribution is included in that month’s return; a month-end contribution compounds from the following month.
What is excluded
Taxes, withholding, fees, commissions, inflation, and variable market returns are not included.
Frequently asked questions
Interpret the compound-growth calculation correctly
How is compound interest calculated?
The calculator converts the effective annual rate you enter into an equivalent monthly rate and applies it to the balance each month. Your monthly contribution is added at the start or end of each month, depending on your selection.
What is the difference between start-of-month and month-end contributions?
A contribution made at the start of the month benefits from that month’s return. A contribution made at month-end starts compounding the following month. This timing changes the result when all other inputs are the same.
Does the calculation include taxes and fund fees?
No. The result is a mathematical scenario based only on the fixed rate you enter. Taxes, withholding, commissions, fund fees, and inflation are not included.
Does the calculated amount guarantee future gains?
No. The rate you enter is an assumption. Actual investment returns can change throughout the period, and you may lose principal.