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? Address Thank you! Oops! Related Contents The Power of Compound Interest Learn how to harness the power of compound interest for your investments. Life and Death of a Twenty Dollar Bill How long does a $20 bill last? What Is My Current Cash Flow? Assess whether you are running “in the black” or “in the red” each month.