Stochastic Oscillator Explained: %K, %D, 5,3,3 vs 14,3,3 and How to Use It

The Stochastic Oscillator answers one question: where did the latest close land inside the recent price range? If it closed near the top of the range, the value is near 100. If it closed near the bottom, it’s near 0. George Lane popularised it, and today it comes with almost every platform. Like every indicator, it is calculated from past prices, so it describes where price is compared with the recent past. It doesn’t tell you where price will go next.

The %K and %D formula in plain words

The main line is called %K.

%K = (Close − lowest Low of the last N bars) ÷ (highest High of the last N bars − lowest Low of the last N bars) × 100

The bottom of the fraction is the height of the range. The top is how far the close sits above the floor of that range. So a reading of 80 means the close is 80% of the way up the range, in the top 20% of the last N bars. That’s all. It doesn’t mean “too expensive” by itself.

The second line, %D, is a simple moving average (SMA) of %K, usually over 3 bars. It’s smoother and slightly slower than %K, and it serves as the signal line.

Fast, slow and the slowing setting

Raw %K straight from the formula jumps around a lot, because one bar closing high or low can move it by dozens of points. That’s why there are two versions.

Version	%K line	%D line
Fast Stochastic	Raw %K from the formula	SMA 3 of raw %K
Slow Stochastic	SMA 3 of raw %K (slowing = 3)	SMA 3 of slow %K

Most traders use the slow version. The three numbers you see on a chart, such as 14, 3, 3, are the range length, the bars used to smooth %K (slowing), and the %D length, in that order. In MT5 the default is %K period 5, %D period 3, slowing 3. 14, 3, 3 is the other widely used set and the one you’ll find in most textbooks.

• 5, 3, 3: short range, fast line, frequent signals, but more false ones
• 14, 3, 3: longer range, calmer line, fewer signals

In TradingView the slowing setting is called %K Smoothing. If it’s set to 1, you’re looking at the fast version.

Worked example, step by step

Say we use a 14-bar range on an example currency pair and look at the last 5 bars. The highest High and lowest Low in the table are the values over the 14 bars ending at that bar.

Bar	14-bar High	14-bar Low	Close	Fast %K
1	1.0950	1.0850	1.0900	50.00
2	1.0950	1.0850	1.0920	70.00
3	1.0960	1.0850	1.0938	80.00
4	1.0960	1.0860	1.0945	85.00
5	1.0980	1.0860	1.0950	75.00

Step 1, fast %K for bar 5: (1.0950 − 1.0860) ÷ (1.0980 − 1.0860) × 100 = 0.0090 ÷ 0.0120 × 100 = 75.00

Step 2, slow %K (average of 3 fast %K values):

• Bar 3: (50 + 70 + 80) ÷ 3 = 66.67
• Bar 4: (70 + 80 + 85) ÷ 3 = 78.33
• Bar 5: (80 + 85 + 75) ÷ 3 = 80.00

Step 3, %D for bar 5: (66.67 + 78.33 + 80.00) ÷ 3 = 75.00

Bar 5 closed higher than bar 4, yet fast %K fell from 85 to 75, because the range got wider (a new High at 1.0980). The Stochastic doesn’t care whether price went up or down. It cares where the close sits in the range. Slow %K still rose to 80 because it also averages the two previous bars. That lag is the price you pay for a smoother line.

A small detail worth knowing: MT5 does the slowing step a little differently from a plain average. It adds up the top of the fraction over 3 bars and divides by the sum of the bottom over 3 bars. In this example that gives 0.0263 ÷ 0.0330 × 100 = 79.70 instead of 80.00. So readings can differ slightly between platforms, but the shape of the line is the same.

Reading the 80 and 20 zones

The standard levels are 80 and 20.

• Above 80 is called overbought. Literally, the close is near the top of the recent range
• Below 20 is called oversold. The close is near the floor of the range

The names make many people think these are reversal signals. They only describe position. In a sideways market, a close near the edge of the range is often where price turns back. In a trending market, closing near the top of the range again and again is simply what a strong uptrend looks like.

%K and %D crosses

The most common signal is the two lines crossing.

• %K crosses up through %D while below 20: momentum starts turning up from the floor of the range
• %K crosses down through %D while above 80: momentum starts turning down from the top of the range

Crosses around 40–60 mean less, because price is in the middle of the range, not near an edge. Also, crosses in the upper zone can repeat several times in a row because the two lines run so close together. In the chart above, the first swing of the range has two cross-downs in the upper zone.

Use it with the trend: only take signals that agree

The thing that makes the Stochastic much more useful is to decide the trend with another tool first, and use the Stochastic only for timing.

1. Read the trend from a higher timeframe or a moving average, for example price above a rising SMA 200 (more in Moving averages)
2. In an uptrend, only pay attention when a pullback takes the Stochastic below 20 and %K then crosses up through %D. Ignore signals from the upper zone
3. In a downtrend, flip it: only pay attention to cross-downs from the upper zone
4. If you can’t tell whether the market is trending or ranging, ADX measures trend strength (see ADX and trend strength)

This series was built to trend up from the start, so it doesn’t prove the rule makes money in real markets. What it shows is the reasoning behind the rule. Counter-trend signals only catch short pullbacks. Signals with the trend get the longer legs while the trend lasts, and if the trend ends, the Stop loss is what limits the damage.

How the Stochastic differs from RSI

The two look alike because both run from 0 to 100 with upper and lower zones, but they measure different things.

	Stochastic	RSI
Measures	Where the close sits inside the recent High–Low range	The balance of up moves against down moves, from each bar’s change in close
Uses	High, Low, Close	Close only
Behaviour	Fast, often swings across the full range	Calmer, reaches the extremes less often
Common levels	80 / 20	70 / 30

A clear example: if today closes only a touch above yesterday but right at the top of the range, the Stochastic jumps close to 100 straight away, while RSI barely moves, because today’s gain was tiny. For RSI in detail, read RSI explained. You don’t need both at once, since they belong to the same family. See why in Combining indicators without redundancy.

When the Stochastic misleads

• Strong trends (embedded readings). The line can stay above 80 or below 20 for dozens of bars, and counter-trend crosses keep appearing, like the 9 cross-downs in the upper zone during the uptrend in the first chart. When the line stays pinned in one zone, read it as a strong trend, not an imminent reversal
• Switching from range to trend. Signals that worked inside the range start failing as soon as price breaks out (read When the market regime changes)
• Very narrow ranges. When High and Low are close together, the bottom of the fraction is tiny, so a small move sends %K from bottom to top. The line looks like a strong signal while price has hardly gone anywhere
• Big news. One unusually long bar widens the range immediately, so readings before and after the news aren’t directly comparable

Stochastic divergence (price makes a new high but the line doesn’t) follows the same idea as RSI divergence and has the same limits. More in Regular and hidden divergence.

The Stochastic tells you where the close sits in the range. It doesn’t tell you whether price is expensive or cheap, or that it is about to turn.

Pairing it with risk management

A Stochastic signal only gives you timing. What keeps you in the game is the plan you make before entering.

• Put the Stop loss where the idea is wrong. If you enter on a cross-up from the lower zone in an uptrend, the idea is wrong once price breaks the low of that pullback. Many traders add a buffer based on volatility, see ATR and Stop loss placement
• Size the position from the Stop loss distance, not from how confident the signal feels. See Position size from Stop loss and Risking 1% per trade
• Don’t close a trade just because the line went above 80. In an uptrend it may stay there for a long time. If you want the Stochastic to help with exits, set the rule in advance and test it first

Common mistakes

• Selling the moment the line goes above 80, or buying the moment it drops below 20, without checking the trend. In a strong trend that’s standing in front of a moving train
• Taking every cross, including crosses in the middle and repeated crosses in the same zone, until you’re overtrading
• Not checking fast vs slow, then comparing readings with someone using the other version
• Tweaking the numbers until the line matches past turning points, which rarely carries into the future
• Stacking Stochastic, RSI and CCI and calling it triple confirmation, when all three measure similar things from the same prices