72法则计算器 — 公式

The Rule of 72

Years to Double ≈ 72 / Interest Rate

This is an approximation. The exact formula is:

Years = ln(2) / ln(1 + r)

The Rule of 72 is most accurate for rates between 6% and 10%.

计算示例

Your investment earns 8% annually.

  1. Rule of 72: 72 / 8 = 9.0 years
  2. Exact: ln(2) / ln(1.08) = 0.6931 / 0.07696 = 9.01 years