Relative Strength Index (RSI) Explained

By Rebecca Lake · August 16, 2023 · 10 minute read

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Relative Strength Index (RSI) Explained

Relative Strength Index, or RSI, is a momentum indicator used to measure a stock’s price relative to itself and its past performance. Developed by technical analyst J. Welles Wilder, the Relative Strength Index focuses purely on individual stock price movements to identify trading trends for a specific security, based on the speed and direction of those price changes.

RSI allows swing investors to compare the price of something to itself, without factoring in the performance of other stocks or the market as a whole. Investors use RSI to pinpoint positive or negative divergences in price for a security or to determine whether a stock is overbought or oversold.

The RSI indicator is useful in technical analysis, which revolves around finding trends in stock movements to determine optimal entry and exit points. Understanding what the Relative Strength Index measures and how it works is central to a technical trading strategy.

What Is RSI in Stocks?

The Relative Strength Index is a rate of change or momentum oscillator that tracks stock price movements. You can visualize it as a line graph that moves up or down, based on a stock’s price at any given time. The Relative Strength Index operates on a scale from 0-100. Where the RSI indicator is within this range can suggest whether a stock has reached an overbought level or if it’s oversold.

RSI is not the same thing as Relative Strength analysis. When using a Relative Strength Comparison (RSC), you’re comparing two securities or market indexes to one another to measure their relative performance.

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How Does the RSI Indicator Work?

The Relative Strength Index operates on a range from 0-100. As stock prices fluctuate over time, the index can move up or down accordingly. Traders typically use the RSI to track price movements over 14 periods (i.e. trading days), though some may use shorter or longer windows of time.

When the RSI indicator reaches 70 or above, it could mean the underlying asset being measured is overbought. An RSI reading of 30 or below, on the other hand, suggests that the asset is oversold. The length of time a stock remains in overbought or oversold territory depends largely on the strength of the underlying trend that’s driving price movements.

The Relative Strength Index can throw off different patterns, depending on whether stocks are in a bull market or bear market. Investors compare the movements of the RSI indicator with actual price movements to determine whether a defined pricing trend actually exists and, if so, in which direction it might be heading. Analyzing moving averages for the stock can help determine the presence of a clear pricing trend.

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RSI Formula

Here’s what the Relative Strength Index formula looks like:

RSI = 100 – (100 / (1 + RS))

In this formula, RS represents the ratio of the moving average of the tracking period’s gains divided by the absolute value of the moving average of the tracking period’s losses.

Here’s another way you might see the Relative Strength Index formula displayed:

RSI = 100 – [100 / ( 1 + (Average of Upward Price Change / Average of Downward Price Change ) ) ]

The RSI formula assumes that you’re able to follow a stock’s pricing changes over your desired tracking period. More importantly than that, however, is knowing how to make sense of Relative Strength Index calculations, which investors often display via a stock oscillator.

Interpreting RSI Results

Reading the Relative Strength Index isn’t that difficult when you understand how the different ranges work. Depending on where the RSI indicator is for a particular stock or market index, it can tell you whether the market is bullish or bearish. You can also use the RSI, along with other technical analysis indicators, to determine the best time to buy or sell.

Above 70

An RSI reading of 70 or higher could indicate that a stock is overbought and that its price might move back down. This could happen through a reversal of the current price movement trend or as part of a broader correction. It’s not unusual for stocks to have an RSI in this range during bull market environments when prices are rising. If you believe that the stock’s price has reached or is approaching an unsustainable level, an RSI of 70 or higher could suggest it’s time to exit.

Below 30

When a stock’s RSI reading is 30 or below, it typically means that it’s oversold or undervalued by the broader market. This could signal a buying opportunity for value investors but it could also indicate the market is turning bearish. It’s more common to see RSI readings of 30 or below during downtrends when stock prices may be in decline across the board.

40 to 90 Range

During bull markets, it’s not uncommon to see the Relative Strength Index for a stock linger somewhere in the 40 to 90 range. It’s less common to see the RSI dip to 30 or below when prices are steadily moving up. An RSI reading of 40 to 50, roughly the middle of the 0-100 scale can indicate support for an upward trend.

10 to 60 Range

In bear markets, or those filled with fear, uncertainty, and doubt, it’s more common to see the Relative Strength Index hover somewhere in the 10 to 60 range. It’s not unusual for stocks to reach 30 or below when the market is already in a downward trend. The middle point of the RSI can act as a support point, though the range shifts slightly to between 50 and 60.

Common RSI Indicators

Relative Strength Index indicators can help investors spot pricing trends. That includes identifying up and down trends, as well as sideways trends when pricing levels consolidate. The reliability of these indicators often hinges on the current phase of a stock or the market as a whole. When reading RSI indicators, it’s important to understand divergence and swing rejections.


A divergence represents a variation or disagreement between the movement of the RSI indicator and the price movements on a stock chart. For example, a bullish divergence means the indicator is making higher lows while the price movement is establishing lower lows. This type of divergence can hint at increasing bullish momentum with a particular stock or the greater market.

A bearish divergence, on the other hand, happens when the indicator is making lower highs while prices are establishing higher highs. This could indicate that investor sentiment is becoming less bullish.

Swing Rejections

A swing rejection is a specific trading technique that involves analyzing RSI movements when pushing above 30 or below 70. Swing rejections can be bullish in nature or bearish.

For example, a bullish swing rejection has four parts or steps:

•   RSI is at an oversold level

•   RSI moves above 30

•   A dip is recorded without rating as oversold

•   RSI passes its recent high

Meanwhile, a bearish swing rejection also has four parts or steps:

•   RSI reaches an overbought level

•   RSI drops below 70

•   RSI hits new highs without dropping back to overbought levels

•   RSI passes recent lows

Swing rejections make it possible to utilize divergence indicators to spot bullish or bearish trends in their earliest stages.

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Is RSI a Good Indicator to Use?

Yes, in certain circumstances. Relative Strength Index can be a good indicator to use in technical analysis, as it can make it easier to detect when a stock or the broader market is overbought or oversold. Understanding how to interpret RSI and its correlation to price movements could help you spot buy or sell signals and detect bull market or bear market trends.

That said, RSI also has some limitations. For example, the RSI can produce false positives or false negatives when bullish or bearish trends don’t align with the way a stock’s price is moving. Like other technical analysis indicators, it’s not an exact way to gauge the market’s momentum. So if stocks are hovering somewhere in the 40 to 60 range, it may be difficult to decipher whether the mood is bearish or bullish.

When using RSI, it’s helpful to incorporate other technical analysis indicators to create a comprehensive picture of the market. Exponential moving average (EMA), for example, is a type of moving average that uses the weighted average of recent pricing data to draw conclusions about the market.

Traders often use RSI in conjunction with other trend indicators, such as the Moving Average Convergence Divergence, the Stochastic Oscillator, or the Volume-Weighted Average Price.


Moving Average Convergence Divergence (MACD) is a technical analysis indicator that investors may use alongside RSI. This indicator can help them determine when to buy or sell, based on the correlation between two moving averages for the same security.

Specifically, it requires looking at a 12-period moving average and a 26-period moving average. To find the MACD line, you’d subtract the 26-period from the 12-period, resulting in a main line. The next step is creating a trigger line, which is the nine-period exponential moving average of the main line. The interactions between these two lines can generate trading signals.

For example, when prices are strongly trending in a similar direction the main line and trigger line tend to move further apart. When prices are consolidating, the lines move closer together. If the main line crosses the trigger line from below, that can produce a buy signal. If the main line crosses the trigger line from above, that can be construed as a signal to sell.

While RSI and MACD are both trend indicators, there are some differences. Relative Strength Index measures the distance between pricing highs and lows. So you’re looking at the average gain or loss for a security over time, which again usually means 14 periods. The MACD, on the other hand, focuses on the relationship between moving averages for a security. It’s a trend-following signal that, like RSI, can indicate momentum.

RSI vs Stochastic Oscillator

The stochastic oscillator is a momentum indicator for technical analysis that shows where a stock’s closing price is relative to its high/low pricing range over a set period of time. The stochastic oscillator can also be used to track pricing for a market index.

Central to the use of the stochastic oscillator is the idea that as a stock’s price increases, the closing price inches closer to the highest point over time. When the stock’s price decreases, the closing price lands closer to the lowest low. Investors use this indicator to determine entry and exit points when making trades.

However, investors interpret RSI and stochastic oscillator readings differently. For example, with a stochastic oscillator, a reading of 20 or below generally means a stock is oversold, versus the 30 or below range for RSI readings. When used together, Relative Strength Index and stochastic oscillators can help with timing trades to maximize profit potential while minimizing the risk of losses.

Can You Use RSI to Time the Crypto Market?

Stocks are not the only asset class for which investors use the RSI. Investors also use the Relative Strength Index to assess conditions in the crypto markets and whether it’s time to sell or continue to HODL.

Cryptocurrency traders may use RSI to gauge momentum for individual currencies. Again, they’re looking at the highs and lows to get a sense of which way prices are moving at any given time. The RSI indicator can help with choosing when to buy or sell, based on previous price movements.

The same rules apply to crypto that apply to stocks: An RSI reading of 70 or above means overbought while a reading of 30 or below means oversold. Likewise, a reading above 50 signals a bullish trend while a reading below 50 can signal a bearish trend. Investors can also use a bearish divergence or bullish divergence to spot a pullback or an upward push.

As with stocks, however, it’s important to remember that RSI is not 100% accurate.

Recommended: Crypto Technical Analysis: What It Is & How to Do One

The Takeaway

RSI can be used to pinpoint positive or negative divergences in price for a stock or to determine whether it’s overbought or oversold. If you’re interested in technical analysis and trending trading, RSI can be a useful metric for making investment decisions.

The RSI is just one tool that you can use to devise a strategy for your portfolio. There are other less technical tools you can use as well when you’re starting to build a portfolio.

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