Rule of 72 Calculator: How Long to Double Your Money
Enter a yearly return to see how long money takes to double, or enter the years to see the return you need. The exact answer is shown next to the shortcut.
- Nothing you type is stored
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- No signup
Doubles in about
9years
- Exact answer
- 9.01 years
- Triples in
- 14.3 years
- In months
- 108 months
- Rule of 72 is off by
- −0.01 years
The rule assumes yearly compounding. It is closest for rates between 6% and 10%.
Show working
- 72 ÷ 8 = 9.00
- Exact: ln 2 ÷ ln(1 + 0.08) = 9.01
How to use
- Choose "Years to double" or "Rate needed".
- Enter the yearly return or the number of years.
- Compare the quick rule-of-72 answer with the exact figure.
Good to know
Years to double ≈ 72 ÷ rate. At 8% money doubles in about 9 years; at 12% in 6. The exact answer is ln 2 ÷ ln(1 + rate), shown alongside so you can see how close the shortcut is.
The rule is most accurate for rates between about 6% and 10%. At very high rates it overstates the time slightly, and at very low rates it understates it. It assumes yearly compounding and a steady rate.
It works for inflation too: at 6% inflation prices double in about 12 years, so a fixed income halves in buying power in that time. The same idea gives the rule of 114 for tripling.
Questions
What is the rule of 72?
A shortcut: divide 72 by the yearly return to get the years needed to double your money.
How long will a PPF deposit take to double?
At 7.1%, about 10.1 years (72 ÷ 7.1); the exact figure is about 10.1 years.
What return do I need to double money in 5 years?
About 14.4% (72 ÷ 5); exactly 14.87%.
Does it work for monthly compounding?
Roughly. For monthly compounding use the effective yearly rate.
Is my data stored?
No. Everything is calculated on your device.