Rule of 72 Calculator
How long will it take my money to double?
The Rule of 72 is a quick mental shortcut: divide 72 by the yearly rate to estimate how long it takes to double your money — or your debt.
How this calculator works
Rule of 72 estimate = 72 ÷ rate. The exact doubling time is ln(2) ÷ ln(1 + rate). The shortcut is most accurate for rates between about 6% and 10%.
Frequently asked questions
Does it work for debt?
Yes. Unpaid credit card debt at 24% roughly doubles in three years — a powerful reason to pay it off fast.
Results are estimates based on the numbers you enter and simplified assumptions. They are not financial advice. See our disclaimer.