Rule of 72 for Compound Interest
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Rule of 72 is a simple fomula to calculate how long will it take for the value of investment to double, given a fixed interest rate.
$ y = i \div r $
Where $ y, i, r $ represent an expected period [year], an investment value [any currency], and a fixed annual interest rate [%] respectedly.
When we invest $100, the calculation results are following:
| Interest rate [%] \ Years | 0 | 1.5 | 3 | 6 | 12 | 24 | 48 | 72 |
|---|---|---|---|---|---|---|---|---|
| 0.0 | 100 | 100 | ||||||
| 1.0 | 100 | 200 | ||||||
| 1.5 | 100 | 200 | ||||||
| 3.0 | 100 | 200 | ||||||
| 6.0 | 100 | 200 | ||||||
| 12.0 | 100 | 200 | ||||||
| 24.0 | 100 | 200 | ||||||
| 48.0 | 100 | 200 |