Money calculator
Compound Interest Calculator
See how savings or investments grow with compounding and regular monthly contributions — with a year-by-year table.
The rule of 72
A quick mental shortcut: divide 72 by the annual percentage rate to estimate how many years it takes money to double. At 7%, that is about 10.3 years; at 9%, about 8. The calculator above gives the precise figure, including the effect of regular contributions — which, over long periods, often matter more than the starting amount.
Educational estimate only — not financial advice. Returns are not guaranteed.
Frequently asked questions
What is the compound interest formula?
For a lump sum, A = P(1 + r/n)^(nt), where P is principal, r the annual rate, n compounding periods per year and t years. Regular contributions are added each period.
Is this financial advice?
No. It is an educational estimate. Real returns vary, and fees and taxes reduce growth.