Finance
Project how an initial balance and recurring monthly contributions can grow over time.
Results update as you type. No calculate button. All calculations run locally in your browser.
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| Amount | |
|---|---|
| Starting principal | — |
| Total contributions | — |
| Interest earned | — |
| Future value | — |
Bars are scaled to the future value. Interest is the remainder after principal and contributions: it grows fastest late in the period, when the balance is largest.
| Year | Balance |
|---|
Contributions are added at the end of each month and interest compounds monthly.
Monthly rate = annual rate ÷ 12. Future value = principal × (1 + monthly rate)months + contribution × [(1 + monthly rate)months − 1] ÷ monthly rate. With a 0% rate, the future value is simply principal + contributions.
Principal $10,000, $500 a month, 6% a year for 10 years (120 months): the principal grows to $18,193.97, the $60,000 of contributions grows to $81,939.67, for a future value of $100,133.64. Interest earned is $30,133.64 on $70,000 put in.
The rate is assumed constant for the whole period, contributions are end-of-month and never missed, and taxes, fees, and inflation are not included. Real returns vary year to year, so treat the result as a projection under one fixed assumption, not a promise.
End of the month, matching the source calculator's convention. Start-of-month contributions would earn one extra month of interest each and give a slightly higher total.
The future value is just principal plus all contributions, with zero interest. The calculator handles that case directly instead of dividing by zero.
Both compound, but time has a distinctive effect: interest earned late in the period applies to a much larger balance, which is why starting earlier often beats contributing more later.
Before tax, and before fees and inflation. A taxable account keeps less than the headline figure.
Not here. Use a constant monthly figure as an average, or split irregular plans into separate runs and add the results.
Results are estimates only and do not constitute professional advice.