Average True Range (ATR) The Average True Range indicator is used to measure the market volatility. The key element in this indictor is the range, and the distinction between periodic low and high is called range. The range can be applied on any trading period, such as intraday or multi-day. In the Average True Range, there is a use of the true range. True range is the biggest of three measures: 1) Current high to low period 2) Previous close to current high period 3) Prior close to currrent etc