ADX: The Trend Strength Indicator

Average Directional Movement Index
The Average Directional Movement Index, or ADX, is a popular trend indicator designed to measure the moving average of price range expansion values. Developed by Welles Wilder, it's one part of the Directional Movement System which aims to measure price movements and their strength.

What is the ADX? The average directional movement index is calculated to reflect the expansion, or contraction, of the price range of a security over a period of time. The traditional setting for the ADX indicator is 14 time periods, but analysts have commonly used the ADX with settings as low as 7 or as high as 30.