This indicator compares recent stock gains to recent stock losses over a certain trading period and converts this observation into a fraction 0 and 100. The calculation is:
RSI= 100- 100/1 + RS
Average Gain= (Total Gains/n)
Average Loss= (Total Losses/n)
RS= (Average Gain/Average Loss)
Where n is the number of periods, typically 14.
Technicians use the RSI to signal for overbought and oversold levels, with 70 being overbought, and 30 being oversold. Divergences in the RSI can also be used to generate signals- an example could be an RSI failing to make new highs while the stock continues to climb higher. This divergence diminishes the strength of the stock’s upward move and could indicate an “extended” security. We use the word could because as with all indicators, the RSI needs to be used in conjunction with other data points to properly evaluate investment decisions.