Rule of 72 Calculator

Approximate doubling time from an annual percent return, or the return needed to double in a set number of years, handy for savings and investing intuition.

The rule of 72 is a rough guide, not a promise. Banks and investments have different compounding schedules; use it to build intuition, not exact projections.

Years to double9 yrs

Frequently Asked Questions

It is a mental math shortcut: dividing 72 by an annual growth rate (in percent) approximates how many years it takes for money to double. It is not exact but is easy to remember.
72 has many divisors (2,3,4,6,8,9,12…) so mental division is easy. For continuous compounding, ln(2) is about 69.3, so 69 or 70 can be slightly more accurate for some rates.
No. You enter a nominal rate. Real purchasing power depends on inflation, and after-tax returns depend on your situation.
See all tools