Candlesticks + ADX: Judging Trend Strength

The Average Directional Index (ADX) comes from J. Welles Wilder’s 1978 book New Concepts in Technical Trading Systems, the same book that introduced RSI and Average True Range. Wilder built it for commodity traders, but it is now used on stocks and every other market. It answers one question:

How strong is the current trend, whichever way it points?

A trend here means price moving mostly one way over several weeks. ADX measures how one-sided that movement has been, on a scale from 0 to 100. It does not say whether the trend is up or down. A steady rally and a steady decline can give the same ADX.

The direction comes from two companion lines, +DI and −DI (the Directional Indicators). Wilder called the whole set his Directional Movement System, and many charting platforms list it as DMI, the Directional Movement Index. On this page, “ADX” means the strength line and “DMI” means all three lines together.

A DMI panel shows three lines, all on the same 0–100 scale:

The rule of thumb: whichever DI line is on top gives the direction, and ADX gives the strength. −DI above +DI with ADX rising is a downtrend getting stronger. −DI above +DI with ADX falling is a downtrend losing strength, as long as ADX was high to begin with; below about 20 there is no real trend to weaken.

You will never need to calculate ADX by hand, but knowing how it is built explains both what it shows and why it is slow. There are four steps:

A worked example of step 1. Yesterday’s high was $51.00 and its low $50.40. Today’s high is $51.20 (an up-move of $0.20) and its low is $49.90 (a down-move of $0.50). The down-move is larger, so today’s −DM is $0.50 and its +DM is zero.

And of step 3. Suppose +DI is 15 and −DI is 35. The gap is 20 and the sum is 50, so DX is 40. Swap them, +DI 35 and −DI 15, and DX is still 40. That is why ADX alone can never tell you which way the trend runs.

The true range in step 2 is the same measure that Average True Range averages. Dividing by it is what puts +DI and −DI on the same 0–100 scale for a $20 stock and a $500 one.

ADX is not a momentum indicator, though some platforms list it as one. Momentum, which MACD and RSI measure, is about how fast price is moving. ADX is about how one-directional the movement has been. A stock can slide steadily, a little each day, and still post a high ADX, because nearly every day makes a lower low and few make a higher high. A choppy slide, where up days keep interrupting the down days, can keep ADX under 20.

Traders mark ADX with a few round numbers. They are habits, not laws, and sources draw them in slightly different places:

Wilder is usually credited with treating an ADX above 25 as a trending market and one below 20 as no trend at all. Many traders use 20 for both. Others call 40, or 50, the start of a very strong trend.

Treat the levels as rough zones, and pay at least as much attention to which way ADX is moving. An ADX of 30 and rising says something different from an ADX of 30 and falling from 45.

A bullish reversal candle only means something after a decline. ADX and the DI lines tell you what kind of decline it was. There are three cases to recognize:

The chart shows the first two cases in order. While the decline turns one-sided, nearly every day a lower low, −DI pulls away from +DI and ADX climbs: the falling-knife stretch. Then the selling slows, and ADX rolls over while price is still at its lows. By the time the Bullish Engulfing prints, ADX has been falling for about a dozen sessions.

For the third case, the Candlesticks + Trading Ranges guide covers how to read a bullish candle inside a sideways box.

When ADX turns down after a strong decline, it is tempting to read it as “the downtrend is over.” It isn’t. A falling ADX only says the trend has become less one-sided. What happens next can go three ways: price turns up, it moves sideways for a while, or the decline resumes after a pause.

The chart above shows why. At the reversal candle, ADX is falling but −DI is still above +DI. By the lines’ own reading, the trend is still down, only weaker. The turn is decided by price: the reversal candle, its confirmation (a later close above the pattern’s high), and in time a higher low.

A reading often traced back to Wilder is that when ADX has climbed above both DI lines and then turns down, the trend often ends or pauses. That is what happens in the chart. Treat it as a sign the trend has stopped strengthening, not as a turn.

When +DI crosses above −DI, up-moves have started to outweigh down-moves over the last few weeks. This is the DMI’s classic buy signal. When −DI crosses above +DI, the reverse.

On its own, a DI cross whipsaws often. A whipsaw is a signal that reverses soon after it fires, catching traders on the wrong side. The DI lines are built from single days’ highs and lows, so one wide up day can lift +DI above −DI and the next down day can push it back. This happens most when ADX is low: with no trend, the two lines sit close together and cross on every small swing.

Wilder himself did not act on every cross. One refinement often credited to him is to wait, after +DI crosses above −DI, until price trades above the high of the crossover day. Many traders also only take crosses while ADX is rising. Neither removes whipsaws; both cut down on them.

In the chart, +DI crosses above −DI a few sessions after the reversal candle. That is normal. The DI lines are smoothed over 14 days, so they usually confirm a turn the candle has already shown.

A bullish reversal candle tells you where and when buyers pushed back. ADX and the DI lines tell you how strong the decline was that they pushed back against. Use them together in three steps:

For example, a Hammer after a long slide, with ADX at 45 and rising and −DI far above +DI, is a candle against a decline that is still gathering strength. The same Hammer with ADX turning down from 45, and −DI sliding toward +DI, is a candle against a decline that has already started to tire. The candle is identical. The context is not.

A Bullish Engulfing or Morning Star ends on a strong up day, which often adds to +DM and lifts +DI a little. That small lift is the candle’s own doing, not proof that the trend has turned. Judge the lines over the days around the candle, not on the candle’s bar alone.

It lags. ADX is smoothed twice. In the chart above, −DI peaks at the end of the fastest drop, but ADX keeps rising for five more sessions and peaks only at the low. In the same way, a new trend can be well under way before ADX rises to confirm it.

It can’t say how far price will go. A high ADX describes the move so far. It is not a target, and a trend can stay strong for longer than a bottom-picker expects.

Its numbers vary between platforms. Some platforms smooth with a standard exponential average instead of Wilder’s method, and ADX depends on how much price history the calculation starts from. Read the shape and the zones, not the exact figure.

ADX doesn’t make a candlestick pattern work. It tells you how strong the decline was that the candle is pushing back against, and whether that decline has started to tire.

So when you check ADX behind a bullish reversal candle, ask one question: “Is the decline still getting stronger?” ADX high and rising with −DI on top says yes, and the candle is fighting a falling knife. ADX turning down with −DI sliding toward +DI says no: the decline is losing force, and the candle is no longer fighting a trend that is still strengthening.

This is one of seventeen context guides in this series: Candlesticks + Moving Averages for trend structure, Candlesticks + RSI for how stretched a move is, Candlesticks + MACD for momentum, Candlesticks + Volume for conviction, Candlesticks + On-Balance Volume for volume flow, Candlesticks + Accumulation/Distribution for where the close fell, Candlesticks + Volume Spread Analysis for reading each bar’s effort and result, Candlesticks + Volume Profile for the prices where volume traded, Candlesticks + Anchored VWAP for the average price paid since a turn, Candlesticks + Fibonacci for retracement levels, Candlesticks + ATR for volatility, Candlesticks + Bollinger Bands for volatility bands around an average, Candlesticks + Multi-Timeframe Analysis for the weekly trend, Candlesticks + 52-Week High/Low for where price sits in its yearly range, Candlesticks + Trend Channels for where in the trend price sits, and Candlesticks + Trading Ranges for sideways markets. New to candles? Start with the candlestick basics guide.