Average True Range

A volatility measurement indicator introduced by J. Welles Wilder in his book: New Concepts in Technical Trading Systems. Wilder originally developed the ATR for commodities but the indicator is also be used for stocks and indices. The ATR measures a commodity or security’s volatility. High ATR values reflects high volatility while low ATR readings indicate range bound movement. True Range is defined as the largest difference of:

-current high minus the current low.
-the absolute value of the current high minus the previous close.
-the absolute value of the current low minus the previous close.

Average True Range (ATR) is a moving average of true range calculated over a series of days.

Average True Range (ATR)
Chart courtesy of Prophet Financial Systems