What does ADX measure?

ADX measures the strength of a trend on a scale of 0 to 100, regardless of direction. A high ADX means a strong trend is in place, up or down, while a low ADX means the market is ranging or directionless. ADX itself never tells you which way price is heading.

What ADX value indicates a strong trend?

A widely used guide is that ADX below 20 to 25 signals a weak or absent trend, readings above 25 indicate a developing trend, and readings above 40 to 50 reflect a very strong trend. These are reference zones, not precise triggers, and the exact thresholds vary by asset and timeframe.

What is the difference between ADX, +DI, and -DI?

ADX measures trend strength only. The +DI and -DI lines, plotted alongside it, show direction: +DI rising above -DI suggests bullish pressure, and -DI above +DI suggests bearish pressure. ADX tells you how strong the trend is; the DI lines tell you which side is winning.

What is the best ADX setting?

Wilder's default is 14 periods, which suits most timeframes. Shorter settings make ADX more responsive but noisier, while longer settings smooth it for position trading. Because ADX is smoothed twice, it lags, so many traders keep the default and use it for confirmation rather than timing.

Can ADX be used for entries?

ADX is better as a filter than a trigger. Traders often require ADX above 25 before taking trend-following signals from other tools, and avoid trend setups when ADX is low and falling. Crossovers of +DI and -DI can flag direction, but they lag and produce false signals in choppy markets.

ADX Indicator: Measure Trend Strength

The Average Directional Index (ADX) is a momentum indicator that measures the strength of a trend on a scale of 0 to 100, without regard to its direction. Developed by J. Welles Wilder Jr. in 1978, ADX helps traders distinguish a strong, tradable trend from a choppy, range-bound market where trend strategies tend to fail.

Key takeaway

ADX measures trend strength, not direction. Readings above 25 suggest a real trend worth following; readings below 20 warn that the market is ranging. Pair ADX with the +DI and -DI lines, or another directional tool, to decide which way to lean.

What is the ADX indicator?

ADX is part of the Directional Movement System that Wilder introduced in New Concepts in Technical Trading Systems (1978), alongside companions like the ATR and RSI. The system has three lines: the Plus Directional Indicator (+DI), the Minus Directional Indicator (-DI), and the ADX itself, which is derived from the other two.

The key idea is separation of concerns. The DI lines handle direction, while ADX strips direction away and reports only how strong the prevailing move is. That is why an ADX of 40 can occur in a powerful uptrend or a powerful downtrend; the number describes conviction, not the side. Treating ADX as a directional signal is the most common way traders misread it.

How is ADX calculated?

ADX is built from directional movement and the true range, then smoothed twice, which is why it lags but stays stable.

The simplified logic runs like this:

+DM = current High - previous High   (if positive and larger than -DM)
-DM = previous Low  - current Low    (if positive and larger than +DM)

+DI = 100 x smoothed(+DM) / ATR
-DI = 100 x smoothed(-DM) / ATR

DX  = 100 x |(+DI) - (-DI)| / |(+DI) + (-DI)|
ADX = smoothed average of DX

In plain terms, the system measures how much price moved up versus down over the period, converts that into the +DI and -DI lines, and then ADX averages the spread between them. A wide, persistent gap between +DI and -DI produces a high ADX; a narrow, flipping gap produces a low one. The default lookback is 14 periods.

How do you read ADX values?

Read ADX as a strength meter. The number tells you whether a trend is worth trading, and the slope tells you whether it is building or fading.

ADX value	Interpretation	Practical read
0 to 20	Weak or no trend	Ranging market, avoid trend setups
20 to 25	Trend emerging	Watch for confirmation
25 to 40	Strong trend	Trend strategies favored
40 to 100	Very strong trend	Strong move, but watch for exhaustion

A rising ADX means the current trend is gaining strength, whichever way it points. A falling ADX means the trend is losing steam, which can precede a range or a reversal. Note that a falling ADX from a high level does not mean price is reversing; it often just means a strong trend is cooling into a steadier one.

How do the +DI and -DI lines work?

The DI lines supply the direction ADX leaves out. When +DI is above -DI, buyers are in control and the trend leans up; when -DI is above +DI, sellers dominate and the trend leans down. A crossover of the two lines is a classic directional signal.

The strongest setups combine both. A +DI crossing above -DI while ADX is rising above 25 is a more convincing bullish signal than either condition alone, because you have direction (the crossover) and conviction (rising ADX) at once. In a flat market with ADX below 20, those same crossovers whip back and forth and tend to be noise.

ADX is a lagging indicator. It is smoothed twice, so it confirms a trend that is already underway rather than predicting one. Do not expect ADX to call a top or bottom; expect it to tell you whether the move you already see has strength behind it.

How do you combine ADX with other tools?

ADX works best as a filter that decides which strategy to run. When ADX is high, trend-following tools earn their keep; when ADX is low, mean-reversion tools tend to do better.

A practical pairing is ADX with moving averages: take moving-average crossover signals only when ADX confirms a trend is present, and stand aside when ADX says the market is ranging. Another pairing is ADX with MACD, using ADX to gauge whether a MACD signal sits inside a real trend or a flat chop. The pattern is always the same: ADX is the gatekeeper that tells your directional tools when their signals are trustworthy.

Common ADX mistakes and limitations

Reading ADX as direction. A high ADX in a downtrend is not bullish. Use the DI lines or price for direction.
Expecting early signals. ADX lags by design. It confirms strength, it does not forecast turns.
Fixed thresholds for every market. The 25 level is a guide; volatile assets and short timeframes may need different cutoffs.
Trading DI crossovers in chop. In low-ADX conditions, crossovers produce frequent false signals.
Ignoring the slope. A high but falling ADX tells a different story than a low but rising one.

Putting ADX in context

ADX answers a question most chart tools skip: is this market trending strongly enough to trade with the trend at all? On its own it is incomplete, since it never points a direction. Combined with the DI lines or a separate directional read, it becomes a disciplined filter that keeps you out of the choppy conditions where trend strategies bleed.

When you are weighing whether a move has real strength, Bullynx's AI trading copilot can read a chart screenshot and talk through what the trend structure and momentum suggest, while you verify the levels. For more momentum tools, see our technical indicators learn hub.

This article is educational and is not financial advice. Indicators describe past and present price behavior, and past or typical indicator behavior does not guarantee future results.

Educational only. Not financial advice. NFA. Bullynx is not a registered investment adviser or broker-dealer. Trading and investing involve significant risk of loss. Read the full risk disclosure.