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The Rule of 72 is a quick mental shortcut for compound growth. Divide 72 by your annual rate of return and you get the approximate number of years for your money to double.
It works well for rates between about 6% and 10% and is useful for comparing investments or for seeing how quickly inflation halves your money's value.
| Annual Return | 8% |
| Years to double (Rule of 72) | 9 years |
| Exact doubling time (compound) | 9.01 years |
| Rule of 70 / Rule of 69.3 | 8.8 / 8.7 years |
| Years to triple (Rule of 114) | 14.3 years |
| Years to grow 4× (Rule of 144) | 18 years |
| ₹1 lakh after 9 years | ₹2 lakh |
Money doubles in about 9 years (exact 9.01 years).
Try this example →| Annual Return | 7.1% |
| Years to double (Rule of 72) | 10.1 years |
| Exact doubling time (compound) | 10.11 years |
| Rule of 70 / Rule of 69.3 | 9.9 / 9.8 years |
| Years to triple (Rule of 114) | 16.1 years |
| Years to grow 4× (Rule of 144) | 20.3 years |
| ₹1 lakh after 10 years | ₹1.99 lakh |
Doubles in about 10.1 years.
Try this example →| Annual Return | 6% |
| Years to double (Rule of 72) | 12 years |
| Exact doubling time (compound) | 11.9 years |
| Rule of 70 / Rule of 69.3 | 11.7 / 11.6 years |
| Years to triple (Rule of 114) | 19 years |
| Years to grow 4× (Rule of 144) | 24 years |
| ₹1 lakh after 12 years | ₹2.01 lakh |
Prices double (money halves in value) in about 12 years.
Try this example →72 divides neatly by many common rates (2, 3, 4, 6, 8, 9, 12), which makes mental math easy. 69.3 is more exact for very low rates.
Yes. Divide 72 by the inflation rate to see how long it takes for prices to double.
It is most accurate for 6–10%. At very high or very low rates the estimate drifts.
Divide 72 by the annual interest rate. At 9%, 72 ÷ 9 = 8 years to double.
About 6 years (72 ÷ 12). The exact compound answer is 6.12 years.