Question: how long does it take to double your money at 5 interest?
Answer: Or, if your money is earning a 5 percent interest rate, you'll double it in 14.4 years (72 divided by 5 equals 14.4). If your money is earning a measly 1 percent interest rate, it will take you—yep, you guessed it—a whopping 72 years to double it. Remember: this is a “rule of thumb,” not an iron-clad law.