The Kelly Formula for Stock Investing is an Excel (.xls) spreadsheet that offers a money management system for stock investing. Once a favorable stock investment opportunity is identified, use the spreadsheet to decide how much of your portfolio to invest. The Kelly Formula results in the maximum expected rate of bankroll growth, and is mathematically the optimal strategy for money management in betting games. The formula gives you that fraction to invest in each stock which maximizes the amount of money you win over a lifetime of investing. This spreadsheet modifies the Kelly Formula to account for the realities of stock market investing.