The Rule of 72 Do you know how long it may take for your investments to double in value? The Rule of 72 is a quick way to figure it out. Related Content Managing the Risk of Outliving Your Money Steps to help you sustain and grow your retirement savings. What Smart Investors Know Savvy investors take the time to separate emotion from fact. Helpful Retirement Strategies for Women Learn how to address the challenges that women face when planning for retirement.