ADX Thresholds: Measuring Trend Strength Without Direction

[Shadow Trader]

The Average Directional Index condenses the difference between positive and negative directional movement into a single line, typically on a 14-bar basis. It measures trend strength, not direction, so a high value can accompany a steady decline just as easily as a steady advance.

Common guidance treats readings under roughly 20 as weak and above roughly 25 as trending, but those figures are conventions rather than laws. Because ADX is itself a smoothed average of smoothed values, it responds slowly. A trend may be well underway before the line rises above a threshold, and the line frequently keeps climbing, or turns down only late, after the strongest portion has passed. A falling ADX from a high level means momentum is slowing, not that price has reversed.

A more careful approach is to use ADX as a regime filter rather than an entry signal, for instance enabling a breakout rule only when the line is rising and disabling a mean-reversion rule under the same condition. Thresholds deserve testing per pair and timeframe, since a level that separates regimes on one chart may separate nothing on another. Slope often adds more than level, because a fixed cut-off applied mechanically tends to confirm trends late.