Average Directional Index
Trend strength gauge — how strongly the market is trending, regardless of direction.
What it is
The Average Directional Index, also from Welles Wilder (1978), is a trend strength indicator. It does not say which way the market is heading — only how strongly it is moving in any direction. ADX = 5 means the market is meandering. ADX = 50 means it is trending hard.
ADX is built on top of two directional movement indicators (DI+ and DI−), which measure upward and downward movement separately. ADX is then a smoothed measure of the magnitude of difference between them. Its brilliance is regime detection: it tells you "trend exists" before you decide whether to trade trend-following or mean-reversion logic.
How it's calculated
For an N-period ADX (default 14), Wilder's process:
1. Compute True Range (TR), +DM (positive directional movement), and −DM for each bar. 2. Smooth each over N bars using Wilder's smoothing (an EMA-like recursive formula). 3. DI+ = 100 × smoothed +DM / smoothed TR 4. DI− = 100 × smoothed −DM / smoothed TR 5. DX = 100 × |DI+ − DI−| / (DI+ + DI−) 6. ADX = N-period smoothed average of DX.
How to interpret signals
Regime detection. ADX < 20 = ranging market (mean-reversion strategies favored). ADX > 25 = trending (trend-following favored). ADX > 40 = strong trend, expect persistence.
Slope. Rising ADX = trend is strengthening. Falling ADX (even from a high level) = trend exhaustion or transition.
Combined with DI+/DI−. When DI+ crosses above DI− with rising ADX, a bullish trend is asserting itself. The symmetric setup is bearish.
Strengths
- Direction-agnostic: tells you whether to trend-trade or mean-revert before you pick a side.
- One of the more reliable regime filters; widely used as confluence in algorithmic strategies.
- Works on any timeframe and asset class with default 14-period.
- Combines magnitude (ADX) and direction (DI+/DI−) in a single conceptual framework.
Limitations
- Lags significantly — by the time ADX crosses 25, the trend is often already mature.
- Wilder smoothing on top of smoothing makes ADX one of the slowest indicators in common use.
- Threshold values (20/25/40) are conventions, not market-specific calibrations.
- Choppy markets with frequent direction changes can keep ADX low even when meaningful moves are happening.
Common pitfalls
- Treating ADX > 25 as a buy signal — it only confirms a trend exists, not which way.
- Comparing raw ADX values across vastly different volatility regimes without context.
- Using ADX to time entries — it is a regime filter, not an entry trigger.
- Demanding ADX > 30 on intraday timeframes — many real intraday trends never reach that level.
Related strategies in Backstrap
Educational note: This page explains what ADX measures and how it is conventionally interpreted. It does not constitute investment advice. Past patterns do not guarantee future results, and no indicator works in all market regimes. See the full disclaimer.
Last updated: 2026-05-08