Overview
ADX answers a question every other trend tool assumes: is the market actually trending? The Average Directional Index measures trend strength — not direction — on a 0–100 scale, while +DI and −DI show which side is winning.
It's the filter that tells you whether to deploy trend tools at all, or switch to range tactics.
Origins & history
- 1978J. Welles Wilder Jr. introduced ADX and the Directional Movement system in New Concepts in Technical Trading Systems, alongside RSI, ATR and Parabolic SAR.1
- BUILT ONIt is built directly on Wilder's Average True Range — directional movement is normalised by ATR.1
How it works
The common reading: ADX > 25 suggests a trend worth following; below ~20 a range. Direction comes from the DI lines. Crucially, ADX itself is non-directional — a high ADX can mean a strong downtrend just as easily as up.1
Market psychology & mechanics
Sustained directional movement is what a real trend looks like mechanically. ADX rises when one side consistently overpowers the other and falls when buyers and sellers trade blows in a range — which is why ADX typically dips at turning points.
Honest assessment
Strengths
A genuinely useful regime filter: it stops you applying breakout tactics in chop and range tactics in a runaway trend. The DI lines add a clean read on who's in control.
Evidence rating: well-constructed and widely used as a filter; it lags and does not predict turns. Its honest job is description (trend vs range), not prediction.
Weaknesses & failure modes
- LAGIt lags. Double-smoothed, ADX confirms a trend well after it began.
- NO DIRECTIONADX alone says nothing about up or down — read the DI lines.
- WHIPSAWDI crosses whipsaw in chop — the very conditions ADX is low in.
- THRESHOLDS25/20 are conventions, not magic levels.
Professional uses vs. retail misuses
How professionals use it
- As a filter: trend tactics only when ADX is rising / > 25.
- Rising ADX to gauge a move has staying power.
- DI lines for directional bias inside that filter.
Common retail misuses
- Trading bare DI crosses in a low-ADX chop.
- Reading high ADX as bullish (it is direction-blind).
- Expecting ADX to call the top or bottom.
Going deeper
ADX pairs with market structure (the visual version of the same question) and ATR (its building block). A common workflow: ADX confirms a trend exists, structure and a moving average give direction, ATR sizes the risk.
Practice
ADX is 35. Is the market bullish?
Unknown from ADX alone. 35 means a strong trend — but possibly strongly down. Check the DI lines: +DI above −DI is bullish.
What does ADX measure?
Trend strength, not direction — how persistently one side overpowers the other, 0–100.
Why does ADX dip at a major turn?
Near a reversal neither side dominates, so directional movement collapses before the new trend asserts itself.
This concept in the knowledge graph
Resources
- TRADERJ. Welles Wilder Jr. — creator of ADX.
- CONCEPTATR & trends.
References (primary where possible)
- J. Welles Wilder Jr., New Concepts in Technical Trading Systems (1978) — overview.
- ADX/DMI calculation & interpretation — StockCharts.