About This Tool
What is Rule of 72 Calculator?
A tool using the Rule of 72 to estimate how long it takes for an investment to double. Also calculates the required interest rate to double within a target period. Useful for quick financial planning.
How to Use
- Select the calculation mode (years to double / rate needed).
- Enter the annual interest rate or target period.
- Click 'Calculate'.
- Compare the Rule of 72 approximation with the precise calculation.
Key Features
- Time-to-double calculation
- Required rate reverse calculation
- Rule of 72 approximation vs. precise calculation comparison
- Intuitive result display
Tips
- Rule of 72: 72 ÷ interest rate (%) = years to double (approximation).
- At 8% annual return, your investment doubles in about 9 years (72÷8).
- This rule is a compound interest approximation — accuracy decreases at higher rates.
Rule of 72 Calculator
Estimate how long for an investment to double
Rule of 72
10.3 years
Precise
10.2 years
Frequently Asked Questions
72法则如何运作？▼
72法则是简单公式：用72除以年利率，估算投资翻倍所需年数。例如年回报率6%：72/6 = 12年翻倍。源自复利公式ln(2)/ln(1+r)，是便捷的心算快捷方式。
72法则有多准确？▼
在6-10%的利率下最准确，误差不到1%。在非常低（1-2%）或非常高（20%+）的利率下精度下降。此工具同时显示72法则估算和精确数学计算以便比较。
有69法则或70法则等替代方案吗？▼
有。69.3法则数学上更精确（因为ln(2) ≈ 0.693），更适合连续复利。70法则有时因简便而使用。72因能被更多数整除（2、3、4、6、8、9、12）而便于心算，因此最受欢迎。