Concept
True Strength Index
True Strength Index is a Momentum & Oscillators concept. The Library holds 3 implementations, each one a working definition you can pull into Quant.
TSI
Top True Strength Index indicators
3 total
What is the True Strength Index?
The True Strength Index (TSI) is a momentum oscillator introduced by William Blau. It starts from one-bar momentum (each close minus the prior close), smooths that series twice with EMAs (commonly 25-period, then 13-period), and divides the result by the same double smoothing applied to the absolute value of the one-bar change. Because that denominator can never be smaller than the absolute value of the numerator, the ratio stays within -1 to +1; multiplied by 100, the output runs between +100 and -100, with zero marking the point where up and down momentum balance.
The ratio is the point of the design: the numerator keeps the sign of price changes while the denominator measures their total size, so TSI reads as net directional momentum as a share of total movement. The deep double smoothing was Blau's device for stripping bar-to-bar noise while keeping the line responsive enough to mark turns, and it gives TSI a smoother trace than most single-smoothed oscillators at comparable settings.
How traders use it
- As a zero-line regime filter: TSI above zero means smoothed up momentum exceeds down momentum over the lookbacks, and many systems only take longs on the positive side and shorts on the negative side.
- As a signal-line system: crossing TSI with a short EMA of itself (often 7 to 13 periods) gives MACD-style timing crosses.
- As a divergence tool: because the line is smooth, its swing highs and lows are well defined, which makes divergences against price easier to mark than on choppier oscillators.
Related concepts · Classic single-name oscillators
Concept family
Momentum & Oscillators
91 concepts mapped · 72 in the Library
True Strength Index FAQ
How is the True Strength Index different from RSI?
Both normalize momentum, but differently. RSI ratios average gains against average losses over one window and reads 0 to 100 around a 50 midline; TSI double-smooths signed price change against absolute price change and reads -100 to +100 around zero. At comparable settings TSI plots smoother, though both lag by construction and neither is predictive on its own.
What are the standard TSI settings?
Blau's published defaults are a 25-period first EMA and a 13-period second EMA, often paired with a 7 to 13 period EMA of the TSI as a signal line. Shorter smoothing makes the line turn faster but whipsaw more; longer smoothing does the reverse. There is no setting that tests best across all markets and timeframes.
Build True Strength Index your way.
Quant writes, tests, and refines it with you — then it runs on LuxAlgo charting or ports to TradingView.