ADX and DMI: trend strength is separate from direction
The Average Directional Index summarizes the separation of positive and negative directional movement.
Before this lesson
These lessons provide background; you can still read this page now.
What the indicator measures
The Average Directional Index summarizes the separation of positive and negative directional movement. Its scale measures strength under that definition rather than bullishness. A strong downtrend can have a high ADX. TradingHub displays ADX together with +DI and −DI, allowing strength and directional comparison to be read separately.
Calculation and units
Positive and negative directional movements compare consecutive high and low extensions, keeping the dominant positive extension and setting the other to zero. After Wilder smoothing, +DI and −DI divide their movements by smoothed true range. DX = 100×absolute(+DI−−DI)/(+DI+−DI); ADX smooths DX again.
Worked educational example
If +DI is 30 and −DI is 10, DX is 50. That does not mean current ADX must also be 50; ADX incorporates a history of DX readings. Swapping the two DI values leaves DX unchanged, demonstrating why a strength number cannot by itself identify upward direction.
Reading it without overclaiming
The conventional threshold 25 is a contextual reference, not a probability of a successful trade. A rising ADX can lag much of an existing move; a falling one does not automatically signal reversal. DI crossings can repeat in ranges. Avoid treating ADX and its components as three unrelated votes.
How TradingHub implements it
The native defaults are period 14 and threshold 25. Its first ADX seed averages DX at indexes N through 2N−1 and is assigned at index 2N; later updates start at 2N+1. This seed alignment can differ from another library. The earlier DI series and ADX warmup are not interchangeable.
Comparisons that matter
Aroon measures recency of extremes, RSI compares gain/loss averages and ADX smooths directional separation. They answer different questions, but still share price inputs. Describe the ADX slope, the DI ordering and their observation times explicitly before suggesting any interpretation.
A reproducible chart review
Open the existing Trading chart and choose the same market, interval and closed observation time as your comparison. Record every calculation parameter before changing one at a time. Match source fields, history length and the bar window. Native indicators calculate from the supplied visible slice; Indicator Studio calculates from its available chart snapshot. A difference after panning may therefore be a window or warmup effect rather than a new market event.
Limits and next lesson
The illustration uses constructed candles, not a dated market observation or a backtest. A live candle can change until it closes. Missing history, volume units and implementation conventions limit comparisons. No indicator guarantees a direction, an execution price or protection from loss. Use the related lessons to separate definitions, observed values and possible explanations; a correct quiz records learning progress, not trading competence.
Knowledge check
Can a strong falling market have high ADX?
- No; ADX is the probability of a rally
- Yes; ADX strength is independent of bullish or bearish direction
- No; high ADX always means rising prices
Show explanation
Direction is studied separately, for example through DI ordering and price structure.
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Primary sources and scope
Educational scenarios are not execution guarantees, forecasts or personal recommendations. Check current product rules at their source.
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