Stochastic oscillator explained: %K, %D, 14-3-3 and crossovers

The Stochastic oscillator tells you where the latest close sits within the recent high-to-low range. A reading of 100 means price closed at the very top of that range, 0 means at the very bottom, and 50 in the middle. Developed by George Lane in the 1950s, it is built on a simple observation: in rising markets closes tend to land near the highs, in falling markets near the lows.

How %K and %D are calculated

The Stochastic has two lines:

• %K = (close − lowest low of the last N candles) / (highest high of the last N − lowest low of the last N) × 100.
• %D = a 3-period simple moving average of %K — a smoothed signal line.

With the common 14, 3, 3 setting:

• 14 is the look-back period N for the high-low range.
• The first 3 smooths raw %K into what is called the "slow" %K.
• The second 3 is the %D average of that slow %K.

If you skip the first smoothing step and use raw %K with a 3-period %D, you get the fast Stochastic. It reacts sooner and produces more crossovers, most of them small. The slow version is simply the fast one with one extra layer of averaging.

A worked example

On USD/JPY M1, over the last 14 minutes the highest high was 150.40 and the lowest low 150.10 — a 30-pip range. The current minute closes at 150.34.

• %K = (150.34 − 150.10) / (150.40 − 150.10) × 100 = 24 / 30 × 100 = 80.

The close sits in the top fifth of the recent range. If the previous two %K values were 72 and 76, %D = (72 + 76 + 80) / 3 = 76, so %K is above %D — upward momentum within the range is still building.

Now suppose the next minute closes at 150.22 with the range unchanged. %K drops to (12 / 30) × 100 = 40. %D becomes (76 + 80 + 40) / 3 = 65.3, and %K has crossed below %D. That is a bearish crossover — and also a good illustration of how fast this oscillator moves: one 12-pip candle took it from 80 to 40.

Overbought, oversold and the 80/20 levels

The usual thresholds are 80 (overbought) and 20 (oversold). As with RSI, these words are misleading. A reading of 90 only says the close is near the top of the last 14 candles' range. In a steady uptrend that is exactly where closes should be, and the Stochastic can sit above 80 for a long time.

Signals tend to be more meaningful when the oscillator leaves an extreme zone rather than when it enters it: %K falling back below 80 after a spell above it, or rising back above 20.

Crossovers

The most common Stochastic signal is %K crossing %D:

• %K crosses above %D, ideally below 20: a possible upturn.
• %K crosses below %D, ideally above 80: a possible downturn.

In the middle of the scale, crossovers are frequent and mostly noise. Even at the extremes, they fail often in trending markets, because a strong trend keeps pushing the close back to the edge of the range.

Stochastic vs RSI

Both are bounded oscillators from 0 to 100 and both use overbought and oversold zones, but they measure different things:

Because the Stochastic includes highs and lows, a long wick changes the range and therefore the reading, even if the close barely moves. RSI ignores wicks. In practice the two often agree, so using both does not double your evidence — see combining indicators. If you want a calmer momentum read, RSI is usually the better choice; if you want a fast read of where price sits inside a range, the Stochastic is.

The Stochastic on short expiries

Its speed is a mixed blessing on short timeframes. On S5–S30 charts, %K can travel from 0 to 100 in a handful of candles, and crossovers appear every few seconds. Some practical adjustments:

• Read it on M1 or M2 while timing on a lower timeframe.
• Use the slow version, or a longer look-back, to reduce small crossovers.
• Favour crossovers that agree with the higher-timeframe direction: in an uptrend, upturns from below 20 rather than downturns from above 80.

Typical mistakes and false signals

• Taking every crossover, especially in the middle of the scale.
• Selling simply because the Stochastic is above 80 in a strong uptrend.
• Using it in a trending market as if it were a range tool. The Stochastic is at its most useful in sideways conditions.
• Treating it as predictive on OTC charts. On Sky Trade, OTC prices are generated by the server, do not track any real market and have an unpredictable next move.

How to add it in the Sky Trade terminal

Open the Indicators menu and switch on Stochastic in the Oscillators group; it appears below the chart with 80 and 20 lines marked. The terminal draws the fast version — raw %K with a 3-period %D — and the look-back period starts at 14 and can be changed with the stepper.