Interest is added every month at the annual rate ÷ 12 and then earns interest itself, which is why growth speeds up over time. Each month the calculator adds interest to the balance and then adds your deposit. The final balance is the result after years × 12 months.
The result is not adjusted for inflation, taxes or fees, and real investment returns vary from year to year, so treat it as an illustration and not a forecast.
Divide 72 by the annual rate to estimate how many years it takes money to double. At 6% that is about 12 years.
Because the later years are calculated on a much bigger balance. Set the years to 30 and then to 20 with the same deposit to see the gap.
No, everything is calculated in your browser.
See also: Loan & Mortgage Calculator · Percentage Calculator