How does the Rule of 72 work?

Divide 72 by the annual percentage return to estimate the years to double. At 8%, money doubles in about 72/8 = 9 years.

When should I use 70 or 69.3 instead?

72 is easiest for mental math and is most accurate around 6–10%. The 70 and 69.3 variants are closer for lower rates and continuous compounding.

Calculadora gratuita da regra de 72. Estime rapidamente os anos necessários para duplicar um investimento dividindo 72 pela taxa anual.

Veja em quantos anos o seu dinheiro duplica com uma dada taxa de juro.

t \approx \frac{72}{r}