True Strength Index

The True Strength Index is a valuable tool for traders as it offers crucial insights into price momentum, trend strength, and possible reversals . . . It assists in identifying trends, detecting overbought or oversold conditions, and generating timely trade signals

11 minutes


Financial analysts often find the True Strength Index (TSI) helpful when analyzing the strength and momentum of price movements in a particular investment. It gives traders and analysts valuable information about whether an asset is experiencing overbought or oversold conditions and can indicate potential trend changes.

The TSI was created by William Blau, a respected trader and author known for his contributions to technical analysis. Blau introduced the TSI in his book “Momentum, Direction, and Divergence” in 1995. It was designed to improve upon existing momentum indicators by providing a more precise representation of price momentum and trend strength. Over time, the TSI has become widely popular among traders and analysts because of its effectiveness in identifying market conditions and generating trading signals.

Based on the concept of moving averages, the TSI calculates the rate of change in price momentum. Unlike other momentum indicators like the Relative Strength Index (RSI), the TSI uses two smoothing periods, which makes it more responsive and accurate in recognizing changes in market conditions.

Traders use the True Strength Index to gain a comprehensive understanding of price momentum, identify potential trend reversals, and ultimately make well-informed trading decisions.

Looking for information on the True Strength Index stock screener? Click here.

Computing the True Strength Index

To calculate the True Strength Index (TSI) using William Blau’s formula, you can follow these steps:

TSI = 100 * (EMA(EMA((PC - PCn), Smoothing Period), Smoothing Period) / EMA(EMA(ABS(PC - PCn), Smoothing Period), Smoothing Period))

In this formula:

  • PC represents the current price (closing price)
  • PCn refers to the price n-periods ago (previous closing price)
  • EMA denotes the Exponential Moving Average
  • Smoothing Period signifies the number of periods employed to smooth the price differences

  1. Start with the current price (closing price), which we’ll call PC.
  2. Take note of the price n-periods ago (previous closing price), referred to as PCn.
  3. Use the Exponential Moving Average (EMA) to smooth the price difference between PC and PCn. This smoothing period helps eliminate noise.
  4. Determine the absolute price difference, denoted as |PC – PCn|.
  5. Apply the EMA again to smooth the absolute price difference.
  6. Divide the value obtained from the first smoothed EMA by the value obtained from the second smoothed EMA.
  7. Multiply the result by 100 to express the TSI as a percentage.

It’s worth mentioning that different analysts or trading platforms may have their own variations or adjustments to the TSI formula. However, the formula provided above follows William Blau’s original formulation.

Understanding the True Strength Index Indicator in technical analysis

To technical analysts, the True Strength Index (TSI) is super important because it gives you valuable insights into the strength and momentum of price movements in a security. Here are some key reasons why the TSI is so important:

Measuring momentum

The TSI helps you measure how fast the prices are moving, so you can tell if they’re speeding up or slowing down. By looking at momentum, you can spot periods of strong price movement and potential changes in the trend.

Overbought and oversold conditions

The TSI helps you identify when the market is overbought or oversold. When the TSI goes above a certain level, it means the security might be overbought, which could signal a correction or a reversal in price. On the other hand, if the TSI falls below a certain level, it suggests the market is oversold, which could be a good time to buy.

Confirming trends

The TSI helps you confirm the direction and strength of a trend. If the TSI is positive and going up, it indicates a bullish trend. If the TSI is negative and going down, it suggests a bearish trend. You can use the TSI to validate trend signals from other indicators or chart patterns.

Spotting divergences

The TSI is useful for finding divergences between the indicator and the price. Divergence happens when the TSI and price move in opposite directions, indicating a possible trend reversal. Bullish divergence occurs when the price makes lower lows while the TSI makes higher lows, suggesting a potential bullish reversal. Bearish divergence happens when the price makes higher highs while the TSI makes lower highs, indicating a potential bearish reversal.

Generating signals

The TSI can generate signals to buy or sell based on crossovers, divergences, or specific levels. Traders often look for TSI line crossovers with a signal line or zero line, as well as bullish or bearish divergences, as triggers to start trading.

Customization and adaptability

You can customize the TSI by adjusting the smoothing period and other parameters to fit your trading style and the characteristics of the security you’re analyzing. This flexibility allows you to use the indicator for different timeframes and market conditions.

In conclusion, the True Strength Index is really important in technical analysis because it gives you a comprehensive view of price momentum, trend strength, overbought/oversold conditions, and potential trend reversals. By using the TSI in your analysis, you can make better-informed trading decisions and improve the accuracy of your strategies.

William Blau’s suggestions on how to use the True Strength Index

True Strength Index plotted along with MA(21) and Donchian Channels indicator

Let’s talk about William Blau, the person who came up with the True Strength Index (TSI), and what he had to say about using it in your trading strategies. Here are some things Blau wanted to share:

Figuring out the trend

Blau suggests that you use the TSI to identify and confirm the current trend. If the TSI values are above zero, it’s a sign of a bullish trend, and if they’re below zero, it indicates a bearish trend. This helps you align your trades with the overall market direction.

Getting trading signals

Blau recommends using a signal line, which is basically a moving average of TSI values, to generate your trading signals. When the TSI crosses above the signal line, it’s a bullish signal, and when it crosses below, it’s a bearish signal. These crossovers can guide your decisions on when to enter or exit a trade.

Understanding extreme market conditions

Blau thinks it’s important to pay attention to TSI levels, specifically +25 and -25, as they could be potential points of reversal. If the TSI crosses above the +25 level, it might mean a price correction or reversal is coming, while crossing below the -25 level could indicate a buying opportunity.

Analyzing divergences

Blau believes that spotting divergences between the TSI and the price can be valuable trading signals. For example, if the price is forming lower lows while the TSI is forming higher lows, it could be a sign of a bullish reversal. On the other hand, if the price is forming higher highs while the TSI is forming lower highs, it could indicate a bearish reversal. Divergences act as early warnings for trend changes.

Looking at different timeframes

Blau suggests analyzing the TSI across different timeframes. Higher timeframes show long-term trends, while lower timeframes offer short-term trading opportunities. This method enables you to make well-informed choices regarding your trades.

Customizing the TSI

Blau encourages you to customize the TSI parameters based on your preferences and the specific security you’re analyzing. Adjusting the smoothing period and threshold levels to match the timeframe and market conditions can be really beneficial.

Considering market volatility

Blau suggests adapting the TSI parameters to account for market volatility. If the market is highly volatile, you may need larger smoothing periods to filter out noise, whereas lower volatility benefits from shorter periods. Adjusting the parameters helps optimize the TSI’s performance.

Confirming with other indicators

Blau emphasizes the importance of confirming TSI signals with other indicators or chart patterns. Moving averages, trendlines, or support and resistance levels can provide validation. When multiple indicators align, it strengthens the signals.

Managing your trades

Blau wants you to focus on proper trade management when using the TSI. Setting stop-loss levels and trailing stop orders to manage your risk and protect your profits is crucial.

Also see: Stop Loss . . . and its importance in tradingSome ways of setting up stop loss levels

Practice and backtesting

Blau advises practicing and backtesting the TSI using historical data. By evaluating its performance and refining your strategies, you’ll gain confidence and understand the strengths and limitations of the TSI under different market conditions.

Blau’s insights show how versatile the TSI is for analyzing trends, identifying overbought or oversold conditions, spotting divergences, and generating signals. You can incorporate these principles into your trading strategies to effectively make use of the True Strength Index.

Advantages & Limitations of the True Strength Index Indicator

Let’s delve into the benefits and limitations of integrating the True Strength Index (TSI) into your trading strategy:


  • Accurate Trend Identification: You can rely on the TSI to accurately recognize and confirm trends. By analyzing TSI values and their correlation with zero or the signal line, you gain valuable insights into the direction and strength of trends. This empowers you to align your trades effectively with the prevailing market momentum.
  • Early Reversal Signals: The TSI is well-known for providing timely signals for potential trend reversals. By observing bullish or bearish divergences between the TSI and price, you can anticipate upcoming shifts in market direction. This enables you to enter or exit positions early and seize profitable opportunities.
  • Customizable Parameters: One key advantage of the TSI is its flexibility in parameter customization. You can adjust parameters like the smoothing period and threshold levels to suit your individual trading style and the specific characteristics of the securities you trade. This adaptability allows you to effectively utilize the TSI across different timeframes and market conditions, enhancing its effectiveness.


  • Lagging Indicator: Similar to many other technical indicators, the TSI exhibits a lagging nature as it relies on historical price data. As a result, it may not provide real-time signals or capture sudden price movements. It’s important to be aware of this limitation and consider complementing the TSI with other indicators or tools to improve its responsiveness to market changes.
  • False Signals in Range-Bound Markets: The TSI may generate false signals, especially when the market is in a range-bound or consolidating phase. During periods of low volatility and limited price movement, the TSI can produce signals that may not accurately reflect the underlying market conditions. You must exercise caution and take additional factors into account when interpreting TSI signals within such market environments.
  • Subjectivity in Parameter Selection: While the TSI allows for parameter customization, selecting the optimal parameters can be subjective and require trial and error. Factors such as the smoothing period, threshold levels, and other parameters significantly impact the TSI’s performance. You need to carefully assess different parameter values and conduct thorough testing to determine the most suitable settings.

It’s crucial to understand these advantages and limitations of incorporating the TSI into your trading strategy. Consider them in conjunction with your risk management approach, overall trading methodology, and other market analysis techniques to optimize your trading outcomes.

By using the TSI, a reliable technical indicator, you can access valuable information about price momentum, trend direction, and potential reversals. With the help of the TSI, you gain the ability to skillfully identify trends, recognize overbought and oversold conditions, and predict when trends might change. The TSI’s flexibility, customizable settings, and ability to provide early signals make it an essential tool for any trader looking for an advantage in the market.

While the TSI is valuable for technical analysis, it’s important not to rely solely on this indicator when making trading decisions. Like any tool, the TSI has limitations and can produce false signals. To make wise trading choices, you should incorporate strong risk management techniques, combine the TSI with other complementary indicators or tools, and conduct a thorough analysis of the market before executing trades. It is strongly recommended to thoroughly test and validate the TSI using historical data before using it for real-time trading. Remember that individual trading outcomes can vary, so it’s necessary to be cautious and diligent when using the TSI or any other trading indicator.

For examples of customizable True Strength Index factory scans that can be edited, modified, or revised, and subsequently scanned through ChartAlert’s native stock screener or technical analysis scanner, click here.

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