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# Aroon Oscillator: Definition, Calculation Formula, Trade Signals

## What Is the Aroon Oscillator?

The Aroon Oscillator is a trend-following indicator that uses aspects of the Aroon Indicator (Aroon Up and Aroon Down) to gauge the strength of a current trend and the likelihood that it will continue.

### Key Takeaways

• The Aroon Oscillator uses Aroon Up and Aroon Down to create the oscillator.
• Aroon Up and Aroon Down measure the number of periods since the last 25-period high and low.
• The Aroon Oscillator crosses above the zero line when Aroon Up moves above Aroon Down. The oscillator drops below the zero line when the Aroon Down moves below the Aroon Up.

## Understanding the Aroon Oscillator

Aroon oscillator readings above zero indicate that an uptrend is present, while readings below zero indicate that a downtrend is present. Traders watch for zero line crossovers to signal potential trend changes. They also watch for big moves, above 50 or below -50 to signal strong price moves.

The Aroon Oscillator was developed by Tushar Chande in 1995 as part of the Aroon Indicator system. Chande’s intention for the system was to highlight short-term trend changes. The name Aroon is derived from the Sanskrit language and roughly translates to “dawn’s early light.”

The Aroon Indicator system includes Aroon Up, Aroon Down, and Aroon Oscillator. The Aroon Up and Aroon Down lines must be calculated first before drawing the Aroon Oscillator. This indicator typically uses a timeframe of 25 periods, however, the timeframe is subjective. Using more periods garners fewer waves and a smoother-looking indicator. Using fewer periods generates more waves and a quicker turnaround in the indicator. The oscillator moves between -100 and 100. A high oscillator value is an indication of an uptrend while a low oscillator value is an indication of a downtrend.

Aroon Up and Aroon Down move between zero and 100. On a scale of zero to 100, the higher the indicator’s value, the stronger the trend. For example, a price reaching new highs one day ago would have an Aroon Up value of 96 ((25-1)/25)x100). Similarly, a price reaching new lows one day ago would have an Aroon Down value of 96 ((25-1)x100).

The highs and lows used in the Aroon Up and Aroon Down calculations help to create an inverse relationship between the two indicators. When the Aroon Up value increases, the Aroon Down value will typically see a decrease and vice versa.

When Aroon Up remains high from consecutive new highs, the oscillator value will be high, following the uptrend. When a security’s price is on a downtrend with many new lows, the Aroon Down value will be higher resulting in a lower oscillator value.

The Aroon Oscillator line can be included with or without the Aroon Up and Aroon Down when viewing a chart. Significant changes in the direction of the Aroon Oscillator can help to identify a new trend.

## Aroon Oscillator Formula and Calculation

The formula for the Aroon oscillator is:

\begin{aligned} &\text{Aroon Oscillator}=\text{Aroon Up}-\text{Aroon Down}\\ &\text{Aroon Up}=100*\frac{\left(25 - \text{Periods Since 25-Period High}\right)}{25}\\ &\text{Aroon Down}=100*\frac{\left(25 - \text{Periods Since 25-Period Low}\right)}{25}\\ \end{aligned}

To calculate the Aroon oscillator:

1. Calculate Aroon Up by finding how many periods it has been since the last 25-period high. Subtract this from 25, then divide the result by 25. Multiply by 100.
2. Calculate Aroon Down by finding how many periods it has been since the last 25-period low. Subtract this from 25, then divide the result by 25. Multiply by 100.
3. Subtract Aroon Down from Aroon Up to get the Aroon Oscillator value.
4. Repeat the steps as each time period ends.

Aroon oscillator differs from the rate of change (ROC) indicator in that the former is tracking whether a 25-period high or low occurred more recently while the latter tracks the momentum by looking at highs and lows and how far the current price has moved relative to a price in the past.

## Aroon Oscillator Trade Signals

The Aroon Oscillator can generate trade signals or provide insight into the current trend direction of an asset.

When the oscillator moves above the zero line, the Aroon Up is crossing above the Aroon Down and the price has made a high more recently than a low, a sign that an uptrend is beginning.

When the oscillator moves below zero, the Aroon Down is crossing below the Aroon Up. A low occurred more recently than a high, which could signal that a downtrend is starting.

## Limitations of Using the Aroon Oscillator

The Aroon Oscillator keeps a trader in a trade when a long-term trend develops. During an uptrend, for example, the price tends to keep achieving new highs which keep the oscillator above zero.

During choppy market conditions, the indicator will provide poor trade signals, as the price and the oscillator whipsaw back and forth.

The indicator may provide trade signals too late to be useful. The price may have already run a significant course before a trade signal develops. The price may be due for a retracement when the trade signal is appearing.

The number of periods is also arbitrary and there is no validity that a more recent high or low within the last 25-periods will guarantee a new and sustained uptrend or downtrend.

The indicator is best used in conjunction with price action analysis fundamentals of long-term trading, and other technical indicators.

Investopedia does not provide tax, investment, or financial services and advice. The information is presented without consideration of the investment objectives, risk tolerance, or financial circumstances of any specific investor and might not be suitable for all investors. Investing involves risk, including the possible loss of principal.

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