Relative strength index (RSI) is a powerful tool in the technical analyst's toolbox. It measures a stock's price change momentum and helps to determine whether a given company has recently been overbought or oversold. Ranging from 0 to 100, the lower the level of the RSI for a particular firm, the more likely that average losses over prior periods have increasingly exceeded average gains.  For many investors, a threshold point of 30 for a company's RSI suggests oversold conditions—and the potential for a tr ...