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 | Have A Question About This Topic? Name Email Address Question Thank you! Oops! Related Contents Once Upon a Goal Do you know how to set up your financial goals for success? This knight does. Life and Death of a Twenty Dollar Bill How long does a $20 bill last? Paying Off a Credit Card Enter various payment options and determine how long it may take to pay off a credit card.