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The Relative Strength Index (RSI) Explained: A Comprehensive Guide


Since its inception, the Relative Strength Index (RSI) has been a widely-used technical analysis indicator among traders and investors. J. Welles Wilder Jr., a mechanical engineer turned technical analyst, introduced the RSI in his groundbreaking 1978 book “New Concepts in Technical Trading Systems.” The book also presented several other innovative technical analysis tools, including the Average True Range (ATR), the Parabolic SAR, and the Average Directional Index (ADX).

Wilder’s work laid the foundation for modern technical analysis and significantly influenced the development of various trading strategies. The RSI was initially designed for use in the commodities market but has since been adapted and applied to multiple financial markets, including stocks, forex, and cryptocurrencies.

The primary purpose of the RSI is to measure the momentum and strength of price movements, helping traders and investors identify overbought and oversold conditions, potential trend reversals, and suitable entry and exit points. As a momentum oscillator, the RSI oscillates between 0 and 100, providing valuable insights into the current market conditions and price dynamics.

What is RSI?

RSI is a momentum oscillator that measures the speed and change of price movements on a scale of 0 to 100. It is valuable for identifying potential trend reversals and market conditions, such as overbought or oversold levels. By comparing the magnitude of recent gains to recent losses, RSI aims to determine whether an asset’s price shows strength or weakness.

Relative Strength Index RSI

How is RSI calculated?

The formula for RSI

The RSI calculation involves a two-step process. First, the average gain and average loss are calculated over a specified number of periods, typically 14. Then, the Relative Strength (RS) is determined by dividing the average gain by the average loss. Finally, the RSI is calculated using the following formula:

RSI = 100 - (100 / (1 + RS))

Example Calculation:

Let’s assume we want to calculate the RSI for a 14-period analysis. The gains and losses for each period are as follows:


Step 1: Calculate the average gain and average loss.

Average Gain = (Sum of Gains over 14 periods) / 14 Average Gain = (2 + 3 + 1 + 4 + 2 + 3 + 1) / 14 Average Gain = 16 / 14 Average Gain ≈ 1.14

Average Loss = (Sum of Losses over 14 periods) / 14 Average Loss = (1 + 2 + 1 + 3 + 1 + 1 + 2) / 14 Average Loss = 11 / 14 Average Loss ≈ 0.79

Step 2: Calculate the Relative Strength (RS).

RS = Average Gain / Average Loss RS = 1.14 / 0.79 RS ≈ 1.44

Step 3: Calculate the RSI.

RSI = 100 - (100 / (1 + RS)) RSI = 100 - (100 / (1 + 1.44)) 

RSI ≈ 59.09

In this example, the RSI is approximately 59.09, indicating a relatively higher average gain compared to the average loss over the 14 periods.

RSI Timeframes

While the default RSI calculation uses a 14-period timeframe, traders can adjust the period to suit their preferences and strategies. Shorter timeframes, such as 9 or 7 periods, make the RSI more sensitive to price changes, generating more signals. Conversely, longer timeframes, such as 21 or 28 periods, reduce sensitivity and produce fewer signals.

Interpreting RSI Values

Overbought and Oversold

When the RSI value rises above 70, it indicates that the asset may be overbought, suggesting a potential price decline. Conversely, an RSI value below 30 signifies oversold conditions, implying a possible price increase. However, these levels should not be taken as absolute buy or sell signals but as indications of potential market conditions that warrant further analysis.

RSI and Divergence

A divergence occurs when the RSI and price action move in opposite directions. Bullish divergence happens when the price forms lower lows while the RSI forms higher lows, indicating potential upward momentum. A bearish divergence occurs when the price forms higher highs, but the RSI forms lower highs, suggesting possible downward momentum. Divergences can help traders identify trend reversals and potential entry or exit points.

Using RSI for Trading 

Entry and Exit Signals

Traders often use RSI to identify possible entry and exit points. For instance, a trader might consider buying when the RSI crosses below the 30 level, indicating a move from oversold territory. Conversely, a trader might sell or short when the RSI crosses above the 70 level, signifying a move from overbought conditions. Additionally, traders may use RSI divergences to time their entries and exits, as described earlier.

Stop Loss and Take Profit

When using RSI to make trading decisions, it’s essential to incorporate risk management techniques, such as setting stop loss and take profit levels. Stop loss orders help limit potential losses, while take profit orders allow traders to lock in gains when the price reaches a predetermined level. Combining RSI signals with appropriate stop loss and take profit levels can help improve overall trading performance.

RSI Limitations and Pitfalls

Despite its popularity, the RSI has some limitations. For example, the indicator can stay in overbought or oversold territory for extended periods during strong trends, leading to false signals and potential losses. Additionally, RSI signals alone may not be sufficient for successful trading, as they don’t provide information about price targets or the overall market context.

Combining RSI with Other Indicators

To overcome some of the RSI’s limitations, traders often combine it with other technical analysis tools to generate more reliable signals and improve decision-making. Moving averages and candlestick patterns are two common tools used in conjunction with RSI.

Moving Averages

Moving averages are popular technical indicators that help smooth out price data and identify trends. There are various types of moving averages, but the most commonly used are the simple moving average (SMA) and the exponential moving average (EMA). The SMA calculates the average price over a specified period, while the EMA gives more weight to recent prices, making it more responsive to recent price changes.

When combining RSI with moving averages, traders can confirm trend direction and generate more reliable entry and exit signals. For example, a trader may look for the following scenarios:

RSI and moving average convergence: If the RSI crosses below the oversold threshold (30) and the price crosses above the moving average, this may indicate a potential long entry signal. Conversely, if the RSI crosses above the overbought threshold (70) and the price crosses below the moving average, this may suggest a short entry signal.

RSI divergence and moving average crossovers: A bullish RSI divergence combined with a bullish moving average crossover (e.g., short-term moving average crossing above the long-term moving average) can strengthen the case for a long entry. Conversely, a bearish RSI divergence combined with a bearish moving average crossover can provide more conviction for a short entry.

Candlestick Patterns

Candlestick patterns are visual representations of price action that can help traders identify market sentiment and potential trend reversals. Some common candlestick patterns include the hammer, doji, engulfing, and harami.

When used alongside RSI, candlestick patterns can help traders better time their entries and exits by confirming overbought or oversold conditions. For example:

Bullish reversal patterns in oversold territory: If a bullish candlestick pattern (e.g., hammer or bullish engulfing) occurs when the RSI is in oversold territory (below 30), this may suggest a potential long entry signal.

Bearish reversal patterns in overbought territory: If a bearish candlestick pattern (e.g., shooting star or bearish engulfing) forms when the RSI is in overbought territory (above 70), this may indicate a potential short entry signal.

Candlestick patterns confirming RSI divergence: When a bullish candlestick pattern accompanies a bullish RSI divergence, it can strengthen the case for a long entry. Similarly, a bearish RSI divergence combined with a bearish candlestick pattern can provide more conviction for a short entry.

By combining RSI with moving averages and candlestick patterns, traders can obtain a more comprehensive view of the market and make more informed trading decisions. This multi-indicator approach can help to filter out false signals, confirm trend direction, and improve overall trading performance.

RSI Variations

Several RSI variations have been developed over the years to address some of the original RSI’s limitations and improve trading performance. Two notable RSI variations are the Modified RSI and the Stochastic RSI.

Modified RSI

The Modified RSI is an adaptation of the traditional RSI formula that incorporates additional factors, such as volatility, to reduce false signals and increase accuracy. This variation adjusts the RSI calculation by considering the asset’s historical volatility, typically measured using the Average True Range (ATR).

By incorporating volatility into the RSI calculation, the Modified RSI can provide a more nuanced view of the market conditions. For example, during periods of high volatility, overbought and oversold thresholds may be adjusted to account for the increased price fluctuations. This can help traders avoid false signals and premature entries or exits.

Stochastic RSI

The Stochastic RSI, developed by Tushar Chande and Stanley Kroll, is an oscillator that measures the RSI’s position relative to its high and low range over a specified period. It combines the features of both the RSI and the stochastic oscillator, providing a more sensitive and potentially more accurate indicator. The Stochastic RSI is calculated using the following formula:

Stochastic RSI = (RSI - RSI_low) / (RSI_high - RSI_low)


  • RSI_low is the lowest RSI value over the specified period.
  • RSI_high is the highest RSI value over the specified period.

The Stochastic RSI ranges between 0 and 1, and traders often multiply the result by 100 to bring the scale to 0-100, similar to the traditional RSI. Like the traditional RSI, overbought and oversold levels can be identified using the 80 and 20 levels, respectively.

By incorporating elements of both the RSI and stochastic oscillator, the stochastic RSI can provide a more sensitive measure of momentum and potential trend changes. However, this increased sensitivity can also result in more false signals, so traders must use additional technical analysis tools and risk management techniques to confirm signals and manage potential losses.

Example scanner based on RSI

"Overbought Weekly RSI" scanner by TrendSpider
“Overbought Weekly RSI” scanner by TrendSpider

The Bottom Line

The Relative Strength Index is a versatile and widely-used technical analysis tool that provides valuable insights into market momentum and potential trend reversals. By understanding its calculation, interpretation, and limitations, traders can use the RSI effectively to make informed trading decisions. Combining the RSI with other technical indicators and risk management techniques can further enhance trading performance and increase the probability of success. While no single indicator guarantees success, the RSI remains a valuable component of many traders’ and investors’ analytical toolkits.


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