How to Use the ADX
To use the average directional index, read it as a strength measure only — it says nothing about direction. Direction comes from the two directional indicator lines plotted with it. Its most useful job is deciding whether conditions suit trading at all.
Most disappointment with this indicator comes from asking it a question it does not answer. It has no opinion about direction and never claimed to.
Before you start
The two directional lines displayed alongside it, not the ADX alone. The main line is built from them, and without them on screen you have strength with no sense of which side it belongs to.
A threshold you have chosen and written down. 25 is conventional. Whatever you pick, pick it before looking at a chart you intend to trade.
A rule for what you do when the reading is low. Usually: nothing. Writing that down is what turns the indicator into a filter rather than a decoration.
The steps
1. Read it as strength only
A high reading means a strong trend in some direction. Down markets produce high readings just as readily as up ones, which surprises people once.
2. Take direction from the two DI lines
The positive line above the negative one indicates upward pressure and the reverse indicates downward. These are the directional half of the tool.
3. Apply your threshold as a filter
Above it, a trend method has conditions to work in. Below it, it does not. 25 is standard because it is widely used, which is a real reason and not a mathematical one.
4. Weight the direction of the reading over its level
A reading rising through 20 says more than one sitting flat at 30. The change describes what is happening; the level describes what has happened.
5. Accept that it confirms rather than warns
The calculation smooths twice, so it is structurally late. It will tell you a trend exists after the trend has been running.
6. Use it to decide whether, not what
It is a permission check placed in front of a method that already has entry rules. It does not supply entries of its own.
7. Stand aside on a low reading
This is the indicator’s most valuable output and the one people ignore. Doing nothing is an instruction, not an absence of one.
8. Remember it cannot see participation
The calculation uses price ranges only. A strong reading built on thin volume is a thin market moving, which is a weaker claim than it appears.
How to tell it worked
Review the last 20 trades your method produced, over at least 60 days.
Count how many were taken with the reading below your threshold. The target is 0 out of 20. Every one above zero is a trade the filter told you to skip and you took anyway, which means the filter is not installed — it is displayed.
Compare the results of trades above the threshold against those below it. If there is no difference across 20 trades, the threshold is not doing work on this instrument and should be changed or dropped rather than kept for appearances.
Then count the days the filter kept you out entirely. A filter that never says no is not filtering, and a reading that is above the threshold constantly means the threshold is too low for this market.
Why the threshold is a convention, not a discovery
There is nothing in the arithmetic that makes 25 meaningful. The number became standard because it was published in the original work and then copied everywhere, which means a great many participants now watch the same line.
That is a real reason to keep it. A level enough people act on becomes partially self-fulfilling, in the same way a widely watched moving average does — and this site’s general position is that a standard value should be kept where it is load-bearing and changed where it is merely inherited.
But it should be said out loud rather than implied. Presenting 25 as though the mathematics produced it is the kind of small dishonesty that makes the rest of an explanation harder to trust.
The original data
Of the 24,971 unique videos in the search study behind this site, 50 have an instruction-shaped title mentioning the ADX, at a median of 17,961 views across 41 channels, with a maximum of 424,723. The ATR, its close relative in construction, appears in 86 instruction-shaped titles at a median of 10,396. Each video is counted once, even when several searches returned it.
50 videos from 41 channels. Like trend lines, this is a subject most creators cover once and move on from — and at a 17,961 median it is better attended than far more heavily produced topics such as the RSI, which has 339 instructional videos at a median of 7,043.
The answer to the question on that chart is that the cross is permission, not an entry. The indicator has told you conditions suit a trend method; it has not told you where to get in, where the stop goes, or which side to take. Treating a threshold cross as a trade is asking a filter to be a strategy, and it is the single most common misuse of this tool.
When it fails
Double smoothing makes it late at both ends, and the second one costs more. It confirms a trend after a good part of the move, which is tolerable. It also stays elevated after the trend has ended, which grants permission to trade a move that is already finished — and because the reading still looks strong, the failure feels like bad luck rather than a structural property of the calculation.
The second failure is a gap inflating the reading. True range includes the gap, so a single jump lifts the strength measure without a trend existing.
A third is asking it for direction. It does not contain that information.
A fourth is trading the threshold cross. It is a filter, not a signal.
A fifth is ignoring a low reading. That output is the most useful one it produces.
And a sixth is treating 25 as derived. It is a convention, and knowing that is part of using it properly.
Related
ADX indicator covers the calculation, the DI lines, and where the smoothing comes from. Trend following is the approach this filter is usually placed in front of. And ATR shares the true-range building block and measures size rather than strength.
I treat it as a filter rather than a signal. Ask it which way to trade and it gives you nothing, because it does not answer that question. Ask it whether the conditions suit a trend method at all and it answers immediately, and it gives permission to do nothing, which most indicators never do.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.