The rule of 72 can instantly calculate how long your money takes to double

The Rule of 72 provides an instant way to visualize the power of compound interest without complex equations. By dividing 72 by a fixed annual percentage yield, such as a 4.20% CD rate, investors can determine that their money will double in approximately 17 years. This mental shortcut accounts for the exponential growth created when interest is earned on prior gains, a mechanic that outpaces simple interest by hundreds of dollars over time.