The classic rule of thumb: divide 72 by your annual rate to estimate how many years it takes to double your money.
Skip complex logarithms — the Rule of 72 is accurate to about 0.3% for rates 6–10%.
We also show the true doubling time using logarithms for comparison.
Flip the rule around to learn what return you need to double money by a target date.
A mental shortcut to compare savings accounts, stocks and inflation instantly.
Put your growth assumptions to the test.