ADX

The Average Directional Index (ADX) is a technical analysis indicator that quantifies the strength of a market trend, independent of its direction. Developed by J. Welles Wilder, it helps traders determine whether a price move is supported by strong momentum or is merely a weak, choppy fluctuation.

How It Works

ADX is derived from the Directional Movement Index (DMI), which consists of two lines: the Positive Directional Indicator (+DI) and the Negative Directional Indicator (-DI). The calculation compares the magnitude of price changes over a set period, usually 14 periods, to produce a value ranging from 0 to 100.

Readings below 20 suggest a weak or non‑existent trend, while values above 25 indicate a strengthening trend. When ADX rises above 40, the trend is considered very strong. The indicator does not specify whether the trend is upward or downward; traders look at the relative positions of +DI and -DI to infer direction.

Why It Matters

Knowing trend strength helps traders avoid false signals and choose appropriate strategies. For example, during a strong uptrend (ADX > 30 with +DI > ‑DI), a trader might favor buying on pullbacks rather than shorting. Conversely, a low ADX suggests a ranging market, where mean‑reversion tactics such as buying near support and selling near resistance may be more effective.

ADX is often paired with other oscillators like the Relative Strength Index (RSI) or Moving Average Convergence Divergence (MACD) to confirm entry and exit points. By filtering out low‑strength moves, ADX improves the reliability of technical trading systems.

• Related terms: RSI, MACD, DMI, Wilder's indicators