Rule of 72 Calculator
Mental math for doubling time
8.0%
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Triple time (Rule 114)
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Quadruple time (Rule 144)
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10× time
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Exact (vs approx)
The inflation warning
Rule of 72 also works backward: at 6% inflation, the rupee halves in buying power every 12 years. If your money sits at 5% FD, you're losing real wealth despite a growing balance.
Related tools
The stockpile of famous rates
Years to double = 72 ÷ annual rate (%).
- 72 ÷ 2% = 36 yrs — savings account
- 72 ÷ 6% = 12 yrs — FD / PPF territory
- 72 ÷ 9% = 8 yrs — gold / balanced funds
- 72 ÷ 12% = 6 yrs — Nifty 50 long-run average
- 72 ÷ 18% = 4 yrs — aggressive equity funds
- 72 ÷ 36% = 2 yrs — high-risk territory
Exact vs Rule of 72: at 8%, exact answer is 9.006 yrs vs Rule of 72's 9 yrs — accurate to within 0.1%. Between 3–15%, the rule is virtually perfect.