True Strength Index TSI
Double-smoothed momentum that cuts noise while keeping direction.
Quick Answer
The True Strength Index double-smooths price change to strip out noise, giving a cleaner read of momentum and direction as it oscillates around zero. A signal-line or zero-line crossover flags momentum shifts, and divergence warns of a fading trend. The heavy smoothing that makes it clear also makes it slower to react on Nifty.
True Strength Index: key takeaways
The TSI is double-smoothed momentum: a clean line that crosses zero for direction and a signal line for entries, with exceptionally clear divergences. It trades speed for smoothness — ideal for trend and swing work, less so for fast markets.
True Strength Index at a glance
| Category | Momentum Indicators |
|---|---|
| Type | Lagging momentum oscillator |
| Created by | William Blau (1991) |
| Best timeframe | Daily and higher for swing/positional |
| Best settings | 25, 13 with a 7–13 signal line |
| Settings to avoid | Expecting fast, early signals — it is smoothed |
| Works best in | Sustained trends |
| Struggles in | Very fast, spiky markets |
True Strength Index in simple words
The TSI takes raw price momentum and smooths it twice with exponential averages, then normalises it. Double smoothing removes most of the jitter that makes indicators like raw Momentum hard to read, leaving a clean line that crosses zero to mark trend changes and crosses a signal line to time entries. It trades some speed for a lot less noise.
True Strength Index — visual
How True Strength Index looks on a chart
True Strength Index: professional explanation
Double smoothing
The TSI smooths the one-bar price change with a long EMA (default 25) and then again with a short EMA (default 13), doing the same to the absolute price change, and takes the ratio × 100. The two-stage smoothing dramatically reduces noise while preserving the underlying momentum trend — the core idea Blau introduced.
Zero line and signal line
Above zero, momentum is net positive; below zero, net negative. A signal line (a short EMA of the TSI) provides crossover triggers much like MACD. Because it is smoothed, its zero-line and signal crosses are cleaner than faster oscillators, at the cost of a little lag.
Divergence strength
Because the TSI is smooth, its divergences against price are unusually clear and are prized as reversal warnings. It behaves like a refined, less noisy MACD, and many traders use it the same way — with the added benefit of a more stable line.
True Strength Index formula
True Strength Index formula
TSI = 100 × EMA₁₃(EMA₂₅(ΔC)) / EMA₁₃(EMA₂₅(|ΔC|))
ΔC is the one-bar change in close. Numerator double-smooths the change; denominator double-smooths its absolute value. Defaults are 25 (long) and 13 (short).
- ΔC — Change in closing price from the previous bar
- EMA₂₅ — First (long) exponential smoothing, default 25 periods
- EMA₁₃ — Second (short) exponential smoothing, default 13 periods
- Signal — A short EMA of the TSI used for crossover triggers
How True Strength Index is calculated
- Compute the one-bar price change ΔC and its absolute value |ΔC|.
- Smooth ΔC with a 25-EMA, then smooth that result with a 13-EMA.
- Do the same double smoothing to |ΔC|.
- TSI = 100 × (double-smoothed ΔC) / (double-smoothed |ΔC|).
- Add a short signal-line EMA and read zero-line and signal crossovers plus divergence.
True Strength Index: interpretation & signals
Traders read the zero line for momentum bias, signal-line crossovers for entries, and the TSI's clean divergences against price for reversal warnings.
Buy / bullish signals
- TSI crosses above its signal line.
- TSI crosses above zero, confirming bullish momentum.
- Bullish divergence against price.
Sell / bearish signals
- TSI crosses below its signal line.
- TSI crosses below zero.
- Bearish divergence against price.
False signals to beware
- Lags at sharp reversals due to double smoothing.
- Signal crosses in a flat market can still whipsaw, though less than faster tools.
- Late to catch fast spikes.
True Strength Index: advantages & limitations
Advantages
- Very low noise thanks to double smoothing.
- Clean zero-line and signal crossovers.
- Exceptionally clear divergences.
- Behaves like a refined MACD.
Limitations & disadvantages
- Lags more than single-smoothed tools.
- Late at sharp turns.
- Less familiar than RSI/MACD.
- Still whipsaws in flat markets, just less.
Combining True Strength Index with other indicators
- Average Directional Index — ADX confirms the trend is strong enough to trust the TSI's smoothed crossovers.
- Relative Strength Index — RSI adds fast overbought/oversold context to the TSI's smoother trend read.
True Strength Index: practical examples (Nifty & Bank Nifty)
NIFTY example
During a steady Nifty uptrend the TSI stays above zero and its signal-line crossovers cleanly mark each pullback-and-continuation, with far fewer false crosses than raw momentum would give. When the TSI finally makes a lower high against a higher price high, the clean divergence warns the trend is maturing.
BANKNIFTY example
Bank Nifty's fast reversals expose the TSI's main weakness: after a violent turn, the double-smoothed line takes several bars to cross zero, so the TSI confirms the new direction late. A trader pairs it with a faster tool for entries and uses the TSI mainly for trend context and divergence.
Common mistakes with True Strength Index
- Expecting it to be fast — it is deliberately smooth.
- Trading it in fast, spiky markets where lag hurts.
- Ignoring divergence, its strongest signal.
- Using it without a trend filter in ranges.
How professionals use True Strength Index
Professionals value the TSI where a clean, low-noise momentum read matters more than speed — swing and positional trading. They use its zero line for bias, signal crossovers for entries in trending conditions, and its unusually clear divergences to anticipate turns, typically alongside a faster tool that handles quick reversals.
True Strength Index: frequently asked questions
What are the default TSI settings?
The standard is 25 (long smoothing) and 13 (short smoothing), with a 7–13 period signal line.
How is the TSI different from MACD?
Both are momentum oscillators with signal lines, but the TSI double-smooths price change and is normalised, giving a cleaner, less noisy line than MACD, at the cost of a little more lag.
Is the TSI leading or lagging?
It is a lagging, smoothed oscillator. Its strength is clarity and low noise, not early signals.
What does the TSI zero line mean?
Above zero, smoothed momentum is net positive (bullish); below zero it is negative (bearish). The zero cross is a trend-bias signal.
Why is the TSI good for divergence?
Because double smoothing removes noise, the TSI's peaks and troughs are clean, making divergences against price unusually clear and reliable as reversal warnings.
True Strength Index: voice-search questions
Natural-language questions people ask about True Strength Index.
What is the True Strength Index in simple words?
It is a smoothed momentum line that crosses zero to show trend direction, with much less noise than basic momentum indicators.
Is the TSI better than MACD?
The TSI is smoother and gives cleaner divergences, while MACD is more widely used and slightly faster; many traders prefer the TSI when noise is a problem.
Sources & references
- William Blau — Momentum, Direction and Divergence (1995)
- Zerodha Varsity — Technical Analysis
Published 7 July 2026. Educational content only — not investment advice.