The rule of 72. You probably already know what it is all about. If not, **the rule of 72 is used as an estimate to determine how long an investment will take to double at any given interest rate.** Let’s say you have $10,000 in a CD that earns 5% annual percentage yield, or APR. How long will it take to reach $20,000? Just take 72 divided by 5, the interest rate on the investment, which equals 14.4 years.

**Of course the rule of 72 is the most popular**, but after running some numbers in a spreadsheet for fun, you can extrapolate even further! I used an 8% return which seemed to be the most accurate in determining the next ‘rule’ of future returns on any given interest rate.

Here’s what I came up with:

*Double your money – rule of 72. Triple your money – rule of 114. Quadruple your money – rule of 144. Quintuple your money – rule of 168. Sextuple your money – rule of 186. Septuple your money – rule of 202. Octuple your money – rule of 216. Nonuple your money – rule of 228. Decuple your money – rule of 240.*

OK, you got me. What I really wanted to do was be the **first personal finance blogger to use the word ‘decuple’ in regards to your investments**. Stupid? Sure. Interesting? You bet!

So if you are looking at getting a return of tenfold or decupling your money, **it will take 30 years with an annual return of 8%** (240 divided by 8). I suppose the first step is to find an investment to lock in a rate over 30 years.* I’m still looking…*

Stupidly Yours,

Matt

I thought decupling your money was just another word for divorce!

That would be ‘decoupling’. I had to use spell checker quite a bit to get all the words right. One letter off and it’s a whole new meaning. ðŸ™‚

These rules don’t hold fast with larger rates of return. With 168 for example, with a 21% ROR, you should be able to get to 5x return by the 8th year. but you only get to 4.59X growth…

@CS

You’re right about not holding entirely true with larger rates of return, but it’s fairly close. Besides, this is more a twist on personal finance, so if you have something that gives fixed 21% return over the life of the investment, please share! ðŸ™‚