Rule of 72 for estimating Investment Returns

I was reminded of the Rule of 72 while checking out the annual returns of some index funds. It is quite a useful formula to quickly get an idea of how long an investment needs in order to double. Below is a more detailed definition I got from Investopedia:

The 'Rule of 72' is a simplified way to determine how long an investment will take to double, given a fixed annual rate of interest. By dividing 72 by the annual rate of return, investors can get a rough estimate of how many years it will take for the initial investment to duplicate itself.

Take note that Rule of 72 becomes less accurate as the rate of return gets bigger. Here is a list of investment instruments, their (rough estimate)  annual rates and the number of years they take to double.

Singapore saving deposit (0.05%pa) - 1440yrs (seriously?)
Singapore Fixed deposit (1.0%pa) - 72yrs
Singapore Saving Bond (2.0%pa) - 36yrs
CPF OA (2.5%pa) - 28.8yrs
CPF SA (4.0%) -  18yrs
STI ETF / High yield bond (6.0%pa) - 12yrs
SPY ETF (12.0%pa) - 6yrs
Quantedge Hedge Fund (24.0%pa) -  3yrs

Take note that the above list is just a rough estimate but you should be able to see how high returns can help to double your investment quicker. Of course, high return entails high risk so please do your own due diligence before embarking in any investments.