Rule of 72 Calculator
Find out how long your money takes to double — or what rate you need to double in X years.
Rule of 72: Years ≈ 72 / annual return (%). A great mental shortcut for rates between 4% and 15%.
Instant Financial Intuition
One of the most useful shortcuts in all of finance: divide 72 by your annual return % to get the number of years it takes to double your money. Works for any compounding investment.
Frequently Asked Questions
What is the Rule of 72?
A mental-math shortcut: Years to double ≈ 72 ÷ annual return %. At 8%, money doubles in 9 years. At 12%, in 6 years.
Is it accurate?
Very accurate between 4% and 15% — within a year or two of the real figure. Outside that range use Rule of 69.3 for continuous compounding or the exact formula.
Why 72 and not some other number?
72 has lots of divisors (2, 3, 4, 6, 8, 9, 12) which makes the mental math easier. Mathematically 69.3 is more accurate, but 72 is close enough and divides cleanly.
How can I use this to set goals?
If you want to double ₹10L in 10 years, you need 72/10 = 7.2% p.a. Index funds (~12%) will do it in 6 years. FDs (~6%) will take 12.