Average Directional Index (ADX): The Trend Strength Indicator

In this article, we will discuss

Average Directional Index - The Trend Strength Indicator - Banner

For any trader, having a deep understanding of the various market trends is crucial for success. Although being aware of the trend's direction is important, knowing its strength is even more crucial.

Entering into a trade without knowing how strong the trend is likely to be could potentially lead to sub-par trading outcomes or even significant losses. Imagine a scenario where you enter a long position thinking that the uptrend is strong, only to later realise that the trend is weak. Such a situation could upend your entire trading strategy and plans.

Here is where the Average Directional Index (ADX) can help. It is a very unique technical indicator that can help you determine trend strength. In this article, we are going to delve into this particular indicator and explore its components, how it is calculated and the ways to interpret and use it.

What is the Average Directional Index (ADX)?

The Average Directional Index was developed in the 1970s by an American mechanical engineer turned real estate developer named J. Welles Wilder Jr. As a part of the Directional Movement System (DMS) family of technical indicators, the ADX measures the strength of a trend, irrespective of its direction.

What are the Components of the ADX Indicator?

The ADX has three primary components - the Positive Directional Indicator (+DI) line, the Negative Directional Indicator (-DI) line and the ADX line. Here is a closer look at each of these components.

  • Positive Directional Indicator (+DI)

The Positive Directional Indicator is a line that measures the strength of upward price movements in an asset. It is calculated by subtracting the previous high from the current high. If the difference between the two highs is positive, it is added to the +DI. However, if the difference is negative, the +DI automatically becomes zero.

The +DI line indicates bullish momentum in the asset. For example, if the +DI line is rising, it indicates the strengthening of bullish momentum, which may eventually lead to an uptrend.

  • Negative Directional Indicator (-DI)

The Negative Directional Indicator is a line that measures the strength of downward price movements in an asset. It is calculated by subtracting the current low from the previous low. If the difference between the two lows is positive, it is added to -DI. If the difference is negative, -DI is automatically set to zero.

The -DI line indicates bearish momentum in the asset. For example, if the -DI line is rising, it indicates the strengthening of bearish momentum that may potentially lead to a downtrend.

  • ADX Line

The ADX line is the most important line of the ADX indicator. It represents the strength of the trend, irrespective of the direction, and is calculated by smoothing out the +DI and -DI lines using the moving average of a specific period. The smoothed-out +DI and -DI lines are then used to determine the ADX.

How is the Average Directional Index (ADX) Calculated?

To arrive at the Average Directional Index for an asset, you need to make a series of calculations. Here is the step-by-step process that you need to follow.

  • Step 1: Calculate the Directional Movement

The first step is to calculate the directional movement of upward and downward price movements. The upward and downward directional movements (+DM and -DM) are calculated using the following formulas.

+DM = Current High - Previous High

-DM = Previous Low - Current Low

  • Step 2: Calculate the True Range (TR)

The True Range (TR) is determined by taking the largest value of the following three values.

- Current High - Current Low

- Current High - Previous Close

- Previous Close - Current Low

  • Step 3: Smooth Out the Directional Movement

Once the directional movements and True Range are calculated, they are smoothed out using a particular period's moving average. Traders usually use 14-day moving averages for smoothing out the values and filtering noise.

  • Step 4: Calculate the Positive and Negative Directional Indexes (+DI and -DI)

Traders use the following formulas to calculate the Positive and Negative Directional Indexes.

+DI = (Smoothed +DM ÷ Smoothed TR) x 100

-DI = (Smoothed -DM ÷ Smoothed TR) x 100

  • Step 5: Calculate the Directional Index (DX)

Once all of the above values are calculated, they are substituted in the below-mentioned formula to calculate the Directional Index.

DX = [(+DI - -DI) ÷ (+DI + -DI)] x 100

  • Step 6: Calculate the ADX

As the name implies, the ADX is an average of the Directional Index over 14 days. It is calculated using the following formula.

ADX = [(Previous ADX x 13) + Current DX] ÷ 14

Interpreting Trend Strength with the Average Directional Index (ADX)

As a trader, knowing how to interpret trend strength using this technical indicator is crucial. Here is a quick overview of how it is done.

The ADX line moves between a scale of 0 and 100, with low ADX values suggesting weak trends and high ADX values suggesting strong trends. Traders often use the threshold values to gain insights into the strength of a trend.

  • ADX value between 20 and 40 indicates a developing trend.
  • ADX value above 40 indicates a strong trend.
  • ADX value below 20 indicates a weak trend.
  • A rising ADX value indicates a trend gaining momentum.
  • A falling ADX value indicates a trend losing momentum.

How to Use the Average Directional Index (ADX)?

Simply being able to interpret the ADX indicator is not enough. You must also know how to use it as part of a trading strategy. Let us explore some of the most common trading strategies and look at how ADX can be incorporated as a part of them.

  • Trend-Following Strategy

A trend-following strategy involves taking up a position in the same direction as the prevailing trend. If you use a trend-following strategy, you must look for rising ADX values, which indicate increasing trend strength. Once the ADX rises above a certain threshold of say 40, you could consider entering into a long or short position depending on the direction of the trend.

  • Counter-Trend Strategy

A counter-trend strategy involves taking up a position against the direction of the prevailing trend. For example, if the prevailing trend is bullish, a counter-trend trading strategy would require you to take up a short position. Traders often use this strategy to cash in on potential trend reversals.

If you use a counter-trend strategy, look for falling ADX values, which indicate weakening trend strength and a possible trend reversal. However, it is important to make sure to confirm the reversal with other technical indicators before taking up a position. This way, you can effectively reduce downside risk.

  • Market-Neutral Strategy

A market-neutral strategy is often used to trade when an asset is range-bound or moving between two ranges with no clear uptrend or downtrend in sight. Consider using market-neutral strategies such as mean reversion trading or range trading if the ADX remains low.

What are the Limitations of the ADX Indicator?

Despite its various advantages, the ADX has its limitations. As a trader, you must know what these drawbacks are so that you can make informed trading decisions. Here are some of the key limitations of this technical indicator.

  • Lagging Technical Indicator

The Average Directional Index is a lagging technical indicator. This essentially means that it provides trading signals based on past price data. Such indicators often confirm trends instead of predicting them and relay delayed information. This delay in feedback from the indicator could potentially lead to suboptimal profits, or in some cases, losses due to late entries or exits.

  • No Indication of Trend Direction

The ADX only gives you information on the strength of a prevailing trend. It does not indicate the direction. Therefore, as a trader, you must use other technical indicators with the directional index to get useful insights on which you can base your trades.

  • May Generate False Signals

The ADX indicator works best in trending markets with high liquidity and volatility. It may not work well in range-bound markets with no clear trend and may generate false trading signals.


The Average Directional Index (ADX) is a very useful indicator that can provide crucial insights into the strength of a trend. However, the indicator has a very limited scope and is not meant to be used alone. As a trader, you may need to pair it with other technical indicators such as Moving Average Convergence Divergence (MACD), Bollinger Bands and Stochastic Oscillators. By combining ADX with other technical indicators, you can not only identify trend strength but also the direction, which can be very valuable when planning a trade.

That being said, it is also important to ensure you use strong risk management practices, such as position sizing and stop-loss, when initiating trades. This will enable you to protect your capital from losses due to adverse or unexpected market movements.

The asset classes and securities quoted in the film are exemplary and are not recommendatory.
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