Fast stochastic oscillator

What the numbers mean

Fourteen is the lookback for %K — where today's close sits within the last 14 bars' high-low range — and 3 is the moving average of %K that forms the %D signal line. 'Fast' means %K is used raw, with no smoothing of its own, which is why the line is so jagged.

• %K 14 — the high-low range lookback
• %D 3 — the moving average of %K that forms the signal line
• 80 / 20 — the conventional overbought and oversold levels
• “Fast” means %K is raw and unsmoothed, which is the entire difference from the slow version

How it is used

Used for overbought and oversold readings (above 80 and below 20) and for %K crossing %D as an entry trigger, mostly in range-bound markets where price genuinely reverts.

• %K crossing %D from below 20 → the classic oversold trigger
• Readings pinned above 80 → a trend, not an opportunity to fade
• Divergence against price → the reading most traders trust more than the crossings

How it relates to everything else

Fast, slow and StochRSI form a ladder of sensitivity built on the same idea. Fast is the raw calculation, slow adds one smoothing pass, and StochRSI applies the whole method to RSI instead of price — each step up in speed brings more signals and more noise.

• Fast → slow → StochRSI: increasingly smoothed, then increasingly derived
• Same 14-bar range that Williams %R uses, on an inverted scale
• Best in ranges; confirm with ADX below 20 before fading extremes

What to watch for

Raw %K whipsaws badly — most traders use the slow version for this reason. In a trend it sits at one extreme for long stretches, so the crossings become noise.