Most volatile stocks are companies that have had the highest price swings during the most recent trading session, leading to a significant gap between these companies' intraday highs and intraday lows. Stocks may see unusually-high price volatility when important new information impacting the stock's valuation is made known to the public, but the market is uncertain how that news will affect the stock's long-term prospects. Price volatility is calculated by dividing the difference between the intraday high and intraday low by a stock's previous closing price.