Brief Description
The True Strength Index (TSI) is a momentum oscillator developed by William Blau and designed to measure the strength and direction of price momentum while filtering out short-term noise. Unlike many momentum indicators that rely on a single smoothing process, the TSI uses double smoothing of price changes, which makes it more stable and less erratic while still responsive to meaningful shifts in market momentum.
TSI oscillates around a zero line and typically ranges between +100 and −100, though actual values often remain within a narrower band. Positive readings indicate bullish momentum, negative readings indicate bearish momentum. The indicator is commonly used across equities, futures, forex, and cryptocurrencies and is adaptable to multiple timeframes.
Formula:
True Strength Index is calculated using the following steps:
1. Price Change (PC)
Price Change (PC):
\(
PC_t = C_t - C_{t-1}
\)
2. Double Smoothed Price Change
An EMA is applied to PC and the result is smoothed again with another EMA.
3. Double Smoothed Absolute Price Change
The same process is applied to the absolute Price Change |PC|.
4. TSI Calculation
True Strength Index (TSI):
\(
TSI_t = 100 \times
\frac{EMA(EMA(PC_t))}
{EMA(EMA(|PC_t|))}
\)
Uses:
1. Identifying Trend Direction and Momentum
One of the most effective uses of the True Strength Index is identifying the dominant momentum bias of the market. When TSI remains above the zero line, bullish momentum is generally in control. When it stays below zero, bearish momentum dominates. The slope of the TSI line provides additional insight. A rising TSI suggests strengthening momentum, even if price movement appears gradual. A flattening or turning TSI can signal slowing momentum before price visibly reacts. This makes TSI particularly useful for confirming trends rather than predicting them.
2. Signal Line Crossovers
TSI is often plotted with a signal line, typically an EMA of the TSI itself. Crossovers between the TSI and its signal line can indicate changes in momentum. When TSI crosses above the signal line, it suggests improving bullish momentum. A crossing below indicates increasing bearish momentum. These signals tend to be smoother and less frequent than those from faster oscillators, which can help reduce whipsaws. They are most effective when aligned with the broader trend and less reliable when used countertrend. In this sense, using TSI together with ADX could enhance trading outcomes.
3. Divergence Analysis
Divergences between price and TSI can highlight potential momentum exhaustion. A bullish divergence occurs when price makes a lower low while TSI forms a higher low, suggesting that downside momentum is weakening. A bearish divergence appears when price reaches a higher high but TSI fails to confirm with a higher peak. Because of its double smoothing, TSI often produces cleaner divergence structures compared to more volatile oscillators, such as the RSI. However, divergences should be interpreted as warnings rather than immediate reversal signals, especially in strong trends.
4. Overbought and Oversold Context
Although TSI does not have fixed overbought or oversold levels, extreme positive or negative readings can indicate stretched momentum. Traders often define custom thresholds based on historical behavior of the asset, such as +25 or −25, to identify areas where momentum may be overextended. In consolidating markets, these extremes can be useful for mean reversion strategies. In trending markets, however, TSI may remain in extreme territory for extended periods, making it more suitable as a context tool than a timing mechanism. Again, ADX readings are of great importance.
Limitations:
01
A Lagging Indicator
The same double smoothing that makes TSI stable also introduces lag. Momentum shifts are often confirmed only after price has already moved. This can delay entries and exits, particularly in fast-moving markets or during sharp reversals. As a result, TSI is better suited for confirmation and trade management than for pinpointing early entries. Moreover, TSI is better suited for larger swings rather than short term trades.
02
Reduced Effectiveness in Choppy Markets
In sideways or low volatility environments, TSI can generate frequent signal line crossovers without meaningful price action. The indicator may oscillate around the zero line, providing little directional clarity and increasing the risk of false signals. Filtering signals using trend identification tools or volatility measures can help mitigate this issue.
03
Subjective Overbought and Oversold Levels
Unlike indicators such as RSI, TSI does not have universally accepted threshold levels. What constitutes an “extreme” reading varies by market, timeframe, and parameter settings. This subjectivity can lead to inconsistent interpretations, particularly for less experienced traders. Improperly chosen thresholds may result in premature countertrend trades or missed opportunities.
