The Rule of 72: how long until your money doubles

The Rule of 72 is a quick mental estimate: divide 72 by your annual return (in %) to get the years until your money doubles.

• 6 % → 72 / 6 = 12 years
• 8 % → 72 / 8 = 9 years
• 4 % → 72 / 4 = 18 years

It shows why a couple of percentage points – and starting early – matter so much over decades.

For the exact figure (not just the estimate), use the savings-plan calculator, or see how yearly cost drags it out in the fee article.

Information only, not investment advice.