The TRIN Arms Index Explained: How to Day Trade Volatility

Regardless of whether you prefer to trade in a low-volatile or high-volatile market, you need to measure volatility.

Traders use technical indicators as the best way to predict the future movements of an asset.

There are hundreds of indicators that are available today. Some of these indicators are provided freely by most trading platforms. Others must be downloaded and installed into these platforms.

At DTTW, our goal is to empower our existing and future traders to become excellent at what they do. As such, we have spent the past few weeks writing in-depth educational articles on technical indicators.

In this article, we will look at the Arms Index, which is not a popular indicator.

What is the Arms Index (TRIN)?

The Arms index is also known as the TRIN or the Short-Term Trading Index. The word TRIN is derived from Trading and Index.

The index was first suggested by Richard Arms in 1967. Richard was a trader and financial researcher, who has published several books on trading.

The indicator is an oscillator and a leading indicator. It is used as an important measure of volatility. In a past article, we just explained what volatility is and how traders identify it.

Importantly, we looked at the CBOE volatility index (VIX), which is one of the most popular measures of volatility. We identified how it is measured and how it is used in the market.

Other indicators that are used to measure volatility are the Bollinger Bands, Envelopes, and the Relative Vigor Index.

How TRIN is Calculated?

The Arms index is calculated by first calculating the advance-decline ratio and then the advance-decline volume ratio. In most cases, these numbers are derived from the data provided by major data providers.

The formula for calculating the index is:

(advances / declines) / (advancing volume / declining volume)

What are these numbers?

Advances is the number of stocks that moved higher in a day while declines are the stocks that declined in the day. Meanwhile, advancing volume is the volume of stocks that gained. Declining volume is the volume of stocks that fell in a day.

Therefore, as this formula suggests, the Arms Index is better used for stocks. At the same time, it is not necessary for you to manually calculate the indicator. Instead, you can just apply it on your charts and then interpret it.

How to Use the Arms Index

There are several methods of using the Arms Index when trading. As mentioned above, you need to ensure that you are trading stocks. This is because the index tells the volatility involved in the stock market.

As such, the signals it generates in other markets may not be very accurate.

An Arms Index value of 1.0 shows that the ratio of AD volume is equal to AD ratio. This means that the market is neutral.

At the same time, an AD value below 1.0 is usually a bullish signal. This is simply because more stocks and their volumes are moving upwards. The opposite is also true. A bearish signal is when the index is above 1.0.

Combining Arms Index with Other Indicators

The best way of using the Arms Index is to combine it with other indicators. The benefit of combining the indicator is to avoid getting a false signal.

As you can see below, the S&P 500 was in an upward trend for the past one year. As it did this, the Arms Index was below 1.0. This is a sign that the strength was strong. This again is confirmed by the double exponential moving averages that have been used.

trin and exponential moving averages

Trin and Exponential Moving Averages


Volatility is an important thing to consider when participating in the financial market. Most traders prefer participating in a low-volatile market while others make more money when there is more volatility.

Knowing how to measure this volatility is an important thing for you to do.

In this article, we have looked at an indicator that is not very popular among participants. This is what makes it unique. Using it can help you become a better trader and anticipate future happenings.

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