Doubling Your Money This calculator demonstrates the power of compound interest. You are viewing this website at a small screen resolution which doesn't support calculators. Click here to view this calculator. Share | Related Content Saving for College 101 Here’s a crash course on saving for college. Pay Yourself First It sounds simple, but paying yourself first can really pay off. Paying Off a Credit Card Enter various payment options and determine how long it may take to pay off a credit card.