This calculator will calculate the growth of an investment. It assumes that the investment will be left alone for the indicated growth time - i.e. no money will be added or taken away from the initial investment. The APR is the annual percentage rate you expect to earn. For example, if you invest $100 and expect to have $105 in one years time, that's an APR of 5%. This is different from the instantaneous interest rate as explained in this document.