💰 Finance
Rule of 72 Calculator
Divide 72 by the annual percentage return and you get the doubling time. It is a mental-maths shortcut, not a formula: the approximation is accurate to within a few tenths of a year for returns between about 5% and 12%, and drifts at the extremes. This page shows both the shortcut and the exact result so you can see the gap.
How it works
Annual rate of return
Starting amount
Years to project
Doubling time (rule of 72)
Doubling time (exact)
Shortcut error
Doublings in the period
Value after the period
Frequently asked questions
How do I use the Rule of 72 Calculator?
Fill in the fields above — the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.