Fast stochastic vs slow stochastic

One extra smoothing pass changes everything

There are two versions of stochastic in the wild. Fast stochastic is what lesson two described: raw %K plus a 3-period SMA of %K as %D. Two lines, one smoothing layer. Slow stochastic adds a second smoothing pass. The fast %D becomes the new slow %K, and a fresh 3-period SMA of that becomes the new slow %D. So slow stochastic is double-smoothed.

The settings string makes the relationship cleaner. Fast stochastic is written as (14, 3). Slow stochastic is written as (14, 3, 3). The third number is the extra smoothing pass. Same 14-period lookback. Same 3-period averaging. One additional 3-period average on top. That is the only structural difference between the two.

Why bother with slow? Because fast stochastic produces a lot of crossover noise. The raw %K reacts to every candle close. Two lines drawn that closely will whip across each other constantly when the market is choppy. Slow stochastic dampens that noise. Crossovers happen less often, but the ones that do happen are more meaningful. Most modern charting platforms default to slow stochastic for exactly this reason.

Practical guidance. On lower timeframes - 5-minute, 15-minute - the fast version is mostly noise unless you have a specific scalping read that uses the speed. On higher timeframes - 4-hour, daily - slow stochastic is the more common choice because each bar already carries more weight and you do not need the indicator to twitch on every close. The default (14, 3, 3) slow setting is a good starting point for almost any chart. Change it only with a clear reason.

Recap: fast stochastic = (14, 3). Slow stochastic = (14, 3, 3). The extra number is one more 3-period SMA pass. Slow has less noise, slightly more lag. Most platforms default to slow.