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Relative Strength Index (RSI) Calculator

Enter your average gain during up periods and average loss during down periods to calculate RSI, Relative Strength, market zone, and gain-to-loss ratio.
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Luis GonzalezCreated by Luis GonzalezLast updated:

How to Use This Calculator

  1. 1

    Enter Average Gain ($)

    Input the average price gain across all 'up' periods within your chosen lookback window. This is the sum of gains divided by the number of periods.

  2. 2

    Enter Average Loss ($)

    Input the average price loss across all 'down' periods in the lookback window. Use the absolute (positive) value of the average decline.

  3. 3

    Specify Lookback Periods

    Enter the number of periods used for the RSI calculation. The standard setting, as introduced by Wilder, is 14 periods.

  4. 4

    Review Your Results

    The calculator will display the RSI value, Relative Strength (RS), market zone (overbought/oversold), and implied win rate.

Example Calculation

A trader wants to calculate the RSI for a stock over 14 periods, where the average gain was $1.20 and the average loss was $0.57.

Average Gain ($)

1.2

Average Loss ($)

0.57

Lookback Periods

14

Results

67.80

Tips

Watch for Divergence

RSI divergence (where price makes a new high/low but RSI doesn't) can signal a potential trend reversal. This is a powerful signal often used by experienced traders.

Adjust Lookback Periods

While 14 periods is standard, shorter periods (e.g., 9) make RSI more sensitive to price changes, while longer periods (e.g., 21) smooth it out, making it less prone to false signals.

Combine with Other Indicators

The RSI is most effective when used in conjunction with other technical indicators, such as moving averages or support/resistance levels, to confirm signals and improve trading accuracy.

Unlocking Market Momentum: The Relative Strength Index (RSI) Calculator

The Relative Strength Index (RSI) Calculator is an essential tool for traders and investors to gauge the momentum of an asset's price action. By inputting the average gain and loss over a specified number of periods, you can instantly compute the RSI value, Relative Strength (RS), and identify whether the market is in an overbought or oversold zone. This powerful oscillator helps in making informed trading decisions, signaling potential reversals or confirming trend strength. For instance, a stock with an average gain of $1.20 and average loss of $0.57 over 14 periods will yield an RSI of 67.80, indicating strong upward momentum.

The Formula Behind Relative Strength Index Calculation

The Relative Strength Index (RSI) is calculated in two main steps. First, the Relative Strength (RS) is determined by dividing the average gain of up periods by the average loss of down periods. Second, this RS value is then plugged into the RSI formula, which normalizes the result to an oscillator ranging from 0 to 100.

The core calculations are:

Relative Strength (RS) = average gain / average loss
RSI = 100 - (100 / (1 + RS))

These formulas, developed by J. Welles Wilder Jr., provide a smoothed average of price changes over a specified lookback period.

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Analyzing Stock Momentum: A Worked Example for RSI

Consider a trader analyzing a tech stock. Over the standard 14-period lookback, the stock had an average gain of $1.20 during its "up" periods and an average loss of $0.57 during its "down" periods. The trader wants to calculate the RSI.

Here's how they would use the calculator:

  1. Input Average Gain: Enter 1.2 for "Average Gain (Up Periods) ($)".
  2. Input Average Loss: Enter 0.57 for "Average Loss (Down Periods) ($)".
  3. Input Lookback Periods: Enter 14 for "Lookback Periods".

The calculator performs these calculations:

  • Relative Strength (RS): $1.20 / $0.57 = 2.10526....
  • RSI: 100 - (100 / (1 + 2.10526...)) = 100 - (100 / 3.10526...) = 100 - 32.203... = 67.796....

The primary output shows an RSI of 67.80, indicating the stock is approaching an overbought condition but still has strong momentum.

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Using RSI to Identify Overbought and Oversold Market Conditions

The Relative Strength Index is a momentum oscillator used by traders and investors to gauge the speed and change of price movements, critically identifying overbought and oversold conditions. An RSI reading above 70 typically signals an overbought market, suggesting that the asset's price has risen too quickly and may be due for a pullback or consolidation. Conversely, an RSI below 30 indicates an oversold market, implying the price has fallen too sharply and might be due for a rebound. These thresholds, widely recognized across global financial markets in 2025, are powerful indicators for potential trend reversals, though they are best used in conjunction with other technical analysis tools for confirmation.

The Origins and Development of the Relative Strength Index

The Relative Strength Index (RSI) was developed by J. Welles Wilder Jr., a mechanical engineer turned real estate developer and technical analyst. He introduced the RSI in his groundbreaking 1978 book, "New Concepts in Technical Trading Systems." Wilder's motivation was to create a momentum oscillator that could more accurately identify overbought and oversold conditions than existing tools, which often produced whipsaws or misleading signals. His meticulous approach to averaging gains and losses over a specific period (standardized at 14 periods) created a robust and widely adopted indicator that remains one of the most popular and influential tools in technical analysis today, nearly five decades after its inception.

Frequently Asked Questions

What is the Relative Strength Index (RSI)?

The Relative Strength Index (RSI) is a momentum oscillator used in technical analysis to measure the speed and change of price movements. It oscillates between 0 and 100, typically indicating whether an asset is overbought (above 70) or oversold (below 30). The RSI helps traders identify potential trend reversals or confirm trend strength by comparing recent gains to recent losses.

What do overbought and oversold mean in RSI analysis?

In RSI analysis, an asset is considered overbought when its RSI value rises above 70, suggesting that the price has increased too rapidly and may be due for a correction or reversal. Conversely, an asset is considered oversold when its RSI falls below 30, indicating that the price has declined too rapidly and may be due for a bounce or reversal. These are not definitive signals but rather probabilities.

How does the 'lookback periods' setting affect the RSI?

The 'lookback periods' setting determines the number of recent price periods (e.g., days, hours) used to calculate the average gains and losses. A shorter lookback period (e.g., 9) makes the RSI more volatile and sensitive to price changes, generating more frequent signals. A longer period (e.g., 21) smooths out the RSI line, making it less sensitive but potentially reducing the number of false signals.