Estimate how long an investment takes to double, triple or quadruple at a given rate, or the rate needed to double in a set time.
The Rule of 72 is a quick mental shortcut: divide 72 by the annual percentage return to estimate the years to double. It is most accurate for returns between about 5% and 12%. The 114 and 144 rules extend it to tripling and quadrupling.
It is a simple way to estimate how long money takes to double at compound interest: just divide 72 by the annual percentage return. At 8% a year, money doubles in about 72 / 8 = 9 years.
It is a close approximation for typical returns of roughly 5% to 12%. At very high or very low rates it drifts from the exact figure, but it is excellent for quick mental maths without a calculator.
They extend the same idea: divide 114 by the rate for the years to triple your money, and 144 for the years to quadruple it.