Rule of 72 Calculator
Estimate how many years it takes an investment — or debt — to double at a given annual rate, using the classic Rule of 72 shortcut alongside the exact compound-interest doubling time.
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Rule of 72 at Common Rates
| Annual Rate | Rule of 72 (Approx.) | Exact Doubling Time |
|---|---|---|
| 2% | 36.00 years | 35.00 years |
| 3% | 24.00 years | 23.45 years |
| 4% | 18.00 years | 17.67 years |
| 6% | 12.00 years | 11.90 years |
| 8% | 9.00 years | 9.01 years |
| 9% | 8.00 years | 8.04 years |
| 10% | 7.20 years | 7.27 years |
| 12% | 6.00 years | 6.12 years |
| 15% | 4.80 years | 4.96 years |
| 20% | 3.60 years | 3.80 years |
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