How to Calculate Daily Stock Return

Find the closing share price of a stock for the current day and the previous day on a financial website, such as Yahoo! Finance, Google Finance or MSN Money. The prices can be found by entering the stock symbol in the 'Get Quotes,' or similarly named, box near the top of the financial website's homepage.
Subtract the previous day's closing price from the current day's close. If the stock increased in value, the number will be positive. A down day will result in a negative number. For example, assume your stock finished yesterday at $24.75 and today the price fell and finished at $22. Subtract $24.75 from $22 to get negative $2.75.
Divide the result by the previous day's close and multiply by 100 to convert to a percentage. Continuing the example, divide negative $2.75 by $24.75 for a result of negative 0.1111. Multiply by 100 to get a daily stock return of -11.11 percent.

How to Chart Volatility for Stock Options

Chart volatility for stock options using the Volatility Charts software available online with TradeKing. This stock options website features stock option analysis software in addition to broker access to stock option contracts. The charting features are free upon sign-up. The Volatility Charts let you graphically display discrepancies between a stock's historical volatility and implied volatility, which are the two key measures of volatility when analyzing stock options. Historical volatility is an analysis of a stock's prior price fluctuations. Implied volatility shows how option prices reflect what market participants expect of the stock's future volatility. These Volatility Charts are easy to access after entering the ticker symbol for the stock.
Create a 'SpreadHacker' chart using the ThinkOrSwim software platform. This software is free after registration and includes many analytical features for researching stock options. The SpreadHacker tool calculates implied volatility, and optionally combines this information with other stock option characteristics, such as strategy probability and real-time price analysis. You can then use this information to find a stock option trading position that suits your investment goals. Hundreds of different stock options trade on most stocks. SpreadHacker lets you categorize the options based on their implied volatility so you can study the possibilities more quickly.
Download the free Stock Volatility Calculator software for Excel. This spreadsheet application includes pre-written formulas to calculate a stock's historical and realized volatility, as well as statistical deviations of the stock's price movements. Unlike more comprehensive software, this program does not incorporate this information into a dedicated interface for stock option analysis. Thus, this program is best suited for veteran traders with a strong knowledge of option behavior. Experts can make informed decisions based solely on these raw calculations and will know how to use this program's data with other software to find good stock option strategies.