The Directional Movement Index (DMI) is a technical indicator developed by J. Welles Wilder in 1978. It is used to identify the direction of price movement and the strength of the trend. Understanding the dmi indicator calculation is essential for traders who want to go beyond simple visual signals and master the mechanics of trend analysis.
DMI Single-Bar Component Calculator
Enter the price data for two consecutive periods to calculate the Directional Movement (+DM, -DM) and True Range (TR).
Note: These are the raw components. For the full DMI/ADX, these values are typically smoothed over a 14-period moving average.
What is the DMI Indicator?
The DMI is actually a collection of three separate indicators combined into one system:
- +DI (Positive Directional Indicator): Measures the strength of upward movement.
- -DI (Negative Directional Indicator): Measures the strength of downward movement.
- ADX (Average Directional Index): Measures the overall strength of the trend, regardless of direction.
The Step-by-Step DMI Indicator Calculation
Calculating the DMI is a multi-step process that involves determining the Directional Movement and the True Range for each period.
Step 1: Calculate Directional Movement (DM)
Directional movement is determined by comparing the current high and low with the previous high and low.
- +DM: Current High - Previous High (If > 0 and > Previous Low - Current Low, otherwise 0).
- -DM: Previous Low - Current Low (If > 0 and > Current High - Previous High, otherwise 0).
Step 2: Calculate True Range (TR)
The True Range is the greatest of the following:
- Current High - Current Low
- |Current High - Previous Close|
- |Current Low - Previous Close|
Step 3: Smooth the Values
Wilder typically used a 14-period smoothing. This is not a simple moving average, but rather a technique where you take the previous smoothed value, subtract 1/14th of it, and add the current period's raw value.
Step 4: Calculate the Directional Indicators (+DI and -DI)
Once you have the smoothed TR, +DM, and -DM, the indicators are calculated as follows:
- +DI = (Smoothed +DM / Smoothed TR) × 100
- -DI = (Smoothed -DM / Smoothed TR) × 100
Interpreting the Results
The DMI provides two primary pieces of information. First, the relationship between +DI and -DI tells you who is in control. If +DI is above -DI, the bulls are in control. If -DI is above +DI, the bears are in control.
Second, the ADX (calculated from these values) tells you the strength of that control. An ADX above 25 generally indicates a strong trend, while an ADX below 20 suggests a range-bound or "choppy" market.
Why Use the DMI Indicator Calculation?
By understanding the math, traders can identify "non-events." For example, if a market makes a new high but the +DM doesn't increase significantly because the range was small, the DMI might signal that the trend is losing steam before the price actually turns around.