Forex Glossary

Accumulative Swing Index (ASI)

The Accumulative Swing Index (ASI) is a technical indicator used in financial market analysis to measure the momentum of a particular asset’s price movements over time. It was developed by Welles Wilder, who also created other popular indicators like the Relative Strength Index (RSI) and the Average Directional Index (ADX).

The ASI takes into account both price and time factors to determine the direction of a security’s trend. It uses the opening price, closing price, high price, and low price of each period to calculate a value that reflects the strength of the trend. The ASI is calculated by taking the previous ASI value, adding or subtracting the current period’s Swing Index, and then multiplying the result by a scaling factor.

The Swing Index is calculated based on the difference between the current period’s high, low, opening, and closing prices. It takes into account the price range of the period and the closing price’s relationship to the period’s midpoint. This value is then used to determine the trend’s direction.

Traders and analysts use the ASI to identify bullish and bearish trends and to determine potential reversal points. A rising ASI suggests a bullish trend, while a declining ASI indicates a bearish trend. Divergences between the ASI and the price of an asset can also signal potential trend changes.

Calculating Accumulative Swing Index

Calculating the Accumulative Swing Index (ASI) involves several steps. Here is a general overview of the process:

Calculate the Swing Index (SI) for each period:

  • a. Calculate the true range (TR) for the period: TR = max(high – low, |high – previous close|, |low – previous close|)
  • b. Calculate the direction of the period: +1 if the current close is higher than the previous close, -1 if it’s lower, and 0 if it’s the same.
  • c. Calculate the raw SI value: RawSI = (close – previous close) + (close – open) / 2 + (previous close – open) / 2
  • d. Calculate the SI value: SI = RawSI / TR * 50 * direction
  • Calculate the ASI value for each period:
  • a. Add the current SI value to the previous period’s ASI value.
  • b. Multiply the result by a scaling factor, which is based on the period’s price range and the previous period’s SI value.
  • c. The resulting value is the current ASI.

The formula for calculating the ASI is as follows:

ASI(current period) = ASI(previous period) + SI(current period) x scaling factor

The scaling factor is calculated using the following formula:

Scaling factor = 0.1 x TR(current period) / SI(previous period) + 0.5

The ASI calculation can be complex, but many trading platforms and charting software programs have built-in ASI indicators that automatically perform the necessary calculations.

Interpreting the Accumulative Swing Index (ASI)

Interpreting the Accumulative Swing Index (ASI) involves understanding the relationship between the ASI and the price of an asset. Here are some general guidelines for interpreting the ASI:

  1. Bullish and bearish trends: A rising ASI suggests a bullish trend, while a declining ASI indicates a bearish trend. Traders may use this information to identify potential buy and sell signals.
  2. Divergences: Divergences between the ASI and the price of an asset can signal potential trend changes. For example, if the ASI is rising while the price is falling, this could indicate a bullish reversal. Conversely, if the ASI is falling while the price is rising, this could indicate a bearish reversal.
  3. Strength of the trend: The magnitude of the ASI value can indicate the strength of the trend. Higher ASI values indicate a stronger trend, while lower values suggest a weaker trend.
  4. Potential support and resistance levels: The ASI can also be used to identify potential support and resistance levels. If the ASI value crosses above a previous peak, this could indicate a breakout and a potential support level. Conversely, if the ASI value falls below a previous trough, this could indicate a breakdown and a potential resistance level.


traders and analysts use the ASI in conjunction with other technical indicators and fundamental analysis to make informed trading decisions. It’s important to remember that no single indicator can predict future market movements with certainty, and traders should always use caution and proper risk management techniques when making trades.

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