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# Average True Range

### From The Free Forex Encyclopedia

Average True Range is one measure of volatility of a given market. The measure was created by J. Welles Wilder, Jr. in his 1979 book “New Concepts in Technical Trading Systems”.

Average True Range is based on the True Range, which is defined as the greatest of three measures:

•The difference between the greatest high and the greatest low

•The absolute value of the current high minus the latest close

•The absolute value of the current low minus the latest close

As a rule, fourteen measurements of the True Range are used in deriving the ATR. These measurements can be taken for four different time intervals: within a day, daily, weekly and monthly. The first ATR in a series is simply the average of the TR for fourteen periods. Future ATRs in the series are derived by the following algorithm:

•Multiply the previous 14-day ATR by 13.

•Add the current ATR.

•Divide the sum by 14.

The measurement is useful due to its sensitivity to large fluctuations in the value of a currency across several periods of measurement, even when the difference between the high and low values for a single period is very small (which would falsely indicate a low overall volatility.)