---
title: "Directional Movement Index: Formula"
description: "J. Welles Wilder's system of the plus directional indicator (+DI), the minus directional indicator (-DI) and the DX/ADX line. It compares successive highs..."
canonical: https://www.getswoopr.com/indicators/trend/directional-movement-index/
source: "Swoopr Investment: https://www.getswoopr.com"
---

## Direct Answer



> Directional Movement Index is a trend measure used to describe trend direction, persistence, strength, or a smoothed price reference. The production page must define the exact calculation convention before interpreting higher or lower readings, because platform and provider implementations can differ.





      


# Directional Movement Index: Formula, Meaning, Signals, Examples and How to Use It



## How Is Directional Movement Index Calculated?

J. Welles Wilder's system of the plus directional indicator (+DI), the minus directional indicator (-DI) and the DX/ADX line. It compares successive highs and lows to measure the direction and strength of a trend.

**Formula:** `DX = 100 * |+DI - -DI| / (+DI + -DI); ADX = smoothed average of DX over n periods`

**Inputs:**

- High, low and close prices
- Smoothing period n (14 is Wilder's default)
- True range and directional movement series

**Worked example.** With a +DI of 30 and a -DI of 15, the DX value is 33.3. The inputs are illustrative numbers, not market data.

**Reading it.** +DI above -DI indicates upward directional movement dominates, and the opposite shows downward dominance. The smoothed ADX shows how strong the trend is, regardless of direction, with values below about 20 often treated as weak trend.

**Limits.** The directional lines cross frequently in non-trending markets, producing false signals. ADX is slow and only rises after a trend is under way.


      

## Indicator overview





| Attribute | Value |
| --- | --- |
| Category | Trend |
| Asset classes | Stocks, ETFs, Indexes, Futures, Forex, Crypto, Commodities |
| Output type | Ratio/index/scalar |
| Parameters | Varies by implementation; document exact settings on use |






## What is Directional Movement Index?



Directional Movement Index is a trend measure used to describe trend direction, persistence, strength, or a smoothed price reference. The production page must define the exact calculation convention before interpreting higher or lower readings, because platform and provider implementations can differ.



For Swoopr, the canonical profile separates definition, calculation, interpretation and decision use. That keeps readers from collapsing a descriptive metric into a trading strategy. An indicator can describe trend, momentum, volatility, participation, positioning or risk without providing a complete entry, exit, sizing or portfolio decision.




## What does it measure?



Directional Movement Index measures specific market properties in the Trend domain. The practical value is repeatability: the same inputs and formula can be applied across a defined dataset, allowing users to compare readings through time or across instruments when the calculation convention is held constant.




## How to read Directional Movement Index



Interpretation depends on the market property being measured. A descriptive reading is not automatically predictive. The same numerical state can lead to different outcomes in a strong trend, quiet range, event-driven gap or illiquid market. Always combine with context from price structure, volume, and broader market regime before drawing conclusions.




## Strengths



- Comparing successive highs and lows separates upward from downward movement, so direction and strength are measured by separate lines.
- Dividing by true range puts the directional lines on a common basis, so they can be compared across instruments.
- Reproducible when the formula and data convention are fixed.




## Weaknesses and limitations



- Directional movement counts only the larger of the up and down extensions, so an inside bar contributes nothing even if its range is wide.
- DX is always non-negative, so it measures the size of directional dominance and cannot show which side is winning without the DI lines.
- Correlated indicators can create false confidence by repeating the same underlying information.




## Editorial and risk note



This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance. Where multiple valid definitions exist, Swoopr states the alternatives and the reason for selecting its primary convention.







## Frequently Asked Questions


        



Is Directional Movement Index a buy or sell signal?




No. +DI above -DI indicates upward directional movement dominates, and the opposite shows downward dominance. The directional lines cross frequently in non-trending markets, producing false signals. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions.










What is the best setting for Directional Movement Index?




Directional Movement Index takes these inputs: high, low and close prices; smoothing period n (14 is Wilder's default); true range and directional movement series. There is no universal best setting for the tunable ones, so test them across instruments, regimes and out-of-sample periods and favor stable parameter regions over one historical winner.










Can Directional Movement Index be used by itself?




The directional lines cross frequently in non-trending markets, producing false signals. ADX is slow and only rises after a trend is under way. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone.










Does Directional Movement Index work on every timeframe?




The calculation (DX = 100 * |+DI - -DI| / (+DI + -DI); ADX = smoothed average of DX over n periods) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it.










Why does Directional Movement Index give false signals?




Directional movement counts only the larger of the up and down extensions, so an inside bar contributes nothing even if its range is wide. DX is always non-negative, so it measures the size of directional dominance and cannot show which side is winning without the DI lines. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated.










How should Directional Movement Index be backtested?




Rebuild Directional Movement Index from high, low and close prices using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline.












S




Swoopr Editorial Team



The Swoopr Editorial Team produces independent investment education, research, and tools for understanding markets, evaluating opportunities, and managing risk. All content is educational only and does not constitute personalized investment advice.



See our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/).