ADX and Trend Strength
ADX measures how strongly a market is trending without saying which way. Its real use is deciding which other indicators are appropriate right now.
MadStockAlerts Research · Updated August 28, 2026
What to take away
- ADX runs 0 to 100 and is directionless.
- Readings below about 20 describe a range; above about 25 describe a trend.
- It is derived from directional movement indicators that do carry direction.
- Its most useful role is choosing between trend tools and range tools.
- It is heavily smoothed, so it confirms a regime rather than anticipating one.
MAD Academy Training Video · 0:45
The Indicator That Tells You Which Indicator to Use
ADX has no direction and that is the point: it answers whether a trend exists, which decides whether your other tools apply.
This lesson is part of a Stock Alerts + Tools plan.
What it measures
The directional movement system compares how much each bar extends beyond the previous bar's range upward against downward. Those become +DI and -DI, which do carry direction. ADX is a smoothed measure of the gap between them, which does not.
A high ADX therefore means one side is consistently winning. It does not say which, and a strong downtrend produces a high ADX exactly as a strong uptrend does. Reading ADX alone as bullish is a category error.
The conventional bands
| ADX | Description |
|---|---|
| Below 20 | No meaningful trend; a range |
| 20 - 25 | Ambiguous; a trend may be forming or fading |
| 25 - 50 | A trend is present |
| Above 50 | A strong trend, historically an unusual reading |
As with every threshold in this pillar these are conventions rather than findings, and they behave differently on different timeframes. An ADX of 22 on a weekly chart is describing something considerably more substantial than the same reading on a five-minute one.
The regime filter
This is where ADX earns its place. Moving-average systems fail in ranges and oscillator systems fail in trends. Neither is broken; each is being used in the regime it was not built for. ADX is a rough answer to which regime is currently present, which makes it a selector for other tools rather than a tool in itself.
- 1Low ADXA range. Oscillators such as RSI and the stochastic are working in the conditions they were designed for.
- 2Rising ADXA trend is establishing. Range tools begin producing losses on every extreme reading.
- 3High ADXA trend is running. Trend tools such as moving averages and MACD are in their conditions.
- 4Falling ADX from a high levelA trend is losing force, which is not the same as reversing.
It is heavily smoothed and therefore slow. It confirms a trend well after the trend began, so it is a description of the current regime and not an early indication of a change in one.
Using it as a filter rather than a signal
ADX measures how directional recent movement has been, without saying which direction. That makes it unusable as an entry and genuinely useful as a condition on other indicators, because most indicators work in one regime and fail in the other.
| ADX | Conventional reading | What tends to work |
|---|---|---|
| Under 20 | No trend | Range techniques: oscillator extremes, mean reversion |
| 20 to 25 | Ambiguous | Little. This is where both families produce false signals |
| 25 to 40 | Trending | Trend techniques: moving averages, breakouts |
| Over 40 | Strong trend | Trend techniques, with the caveat that extremes do not persist |
The value of the filter is that it removes a specific and common error: applying a mean-reversion rule during a trend, or a trend-following rule during a range. Both fail reliably in the wrong regime, and the regime is the thing ADX is measuring.
ADX is heavily smoothed and therefore lags substantially. It confirms that a trend has been in place rather than that one is beginning, which limits it to a filter and rules it out as a timing tool.
What DI+ and DI- add
ADX is normally plotted with two companion lines, the positive and negative directional indicators, and the three are computed together. ADX itself is derived from the difference between them, which is why it carries strength without direction.
ADX is a smoothed average of |DI+ - DI-| / (DI+ + DI-)
- DI+ measures the share of recent movement that was upward
- DI- measures the share that was downward
- taking the absolute difference is what discards the direction
Reading the two directional lines alongside ADX restores the direction that ADX deliberately removes. DI+ above DI- with a rising ADX describes a strengthening uptrend; the same ADX with DI- on top describes a strengthening decline, and the ADX line is identical in both cases.
A falling ADX does not mean a reversal. It means the trend is becoming less directional, which is equally consistent with a pause, a range, or a slow drift in the same direction. Reading it as a sell signal is reading direction into a measure built to exclude it.