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Technical indicators
Stochastic Oscillator and Stochastic RSI: Reading %K and %D
The stochastic oscillator is a momentum indicator developed by George Lane. %K compares the latest close with the highest high and lowest low of the last 14 periods, scaled from 0 to 100, and in the standard form %D is a 3-period simple moving average of %K. Readings describe recent price position, not future moves.
In brief
What is the stochastic oscillator?
The stochastic oscillator compares where a close sits within its recent high-low range. Here is how %K and %D are calculated, a worked example, how the fast, slow and full forms differ, and how Stochastic RSI applies the same formula to RSI.
Key takeaways
- %K = (C minus LL) divided by (HH minus LL), multiplied by 100, over a 14-period look-back. %D is a 3-period simple moving average of %K in the StockCharts default.
- The fast, slow and full forms differ in how much smoothing they apply before %K and %D are drawn. StockCharts gives 14, 3, 3 as the full-form defaults: look-back, %K smoothing and %D period.
- The 80 and 20 levels are conventional markers on the 0 to 100 scale, which places them at the top and bottom fifths of the look-back range. They describe position, not timing.
- Stochastic RSI applies the same range formula to RSI values, and StockCharts shows it on a 0 to 1 scale, so check the scale before comparing readings.
- The stochastic oscillator uses past prices only. It cannot show whether a move will continue, and its readings depend on the settings you choose.
What the stochastic oscillator measures
The stochastic oscillator is a momentum indicator that George Lane developed in the late 1950s, according to StockCharts ChartSchool. The indicator turns the position of the close within the recent range into a number between 0 and 100.
It describes where the latest close sits inside a fixed look-back window. For a different momentum approach, read what is MACD, which compares two moving averages instead of a price range.
The %K and %D formulas
- %K: (C minus LL) divided by (HH minus LL), multiplied by 100. C is the latest close, HH is the highest high and LL is the lowest low over the look-back period.
- %D: a 3-period simple moving average of %K in the StockCharts form. Some platforms let you choose the averaging method.
| Reference | %D method | Defaults printed | Scale |
|---|---|---|---|
| StockCharts ChartSchool (Fast, Slow and Full) | Simple moving average (SMA) of %K | 14, 3 (Fast and Slow); 14, 3, 3 (Full) | 0 to 100 |
| MetaTrader 5 help (Stochastic Oscillator) | Exponential, Simple, Smoothed or Weighted, chosen in the %D method input | None printed on the help page | Not stated on the page |
Sources: StockCharts ChartSchool, Stochastic Oscillator Fast, Slow, and Full; MetaTrader 5 help, Stochastic Oscillator. Checked 10 November 2026.
The variants above differ in %D method, printed defaults and scale, so check the settings on your own platform before comparing readings.
Stochastic oscillator worked example
This is an Example with invented numbers, not market data. Over the last 14 bars the highest high is 120 and the lowest low is 100, so the range is 20 points. The latest close is 105.
Example: %K = (105 minus 100) divided by (120 minus 100), multiplied by 100 = 5 divided by 20, multiplied by 100 = 25. The close sits 25% of the way up the range, so %K reads 25.
Example: for %D, take the last three %K values, which are 35, 30 and 25 in this Example. Their average is (35 + 30 + 25) divided by 3 = 30, so %D is 30. Here %K sits below %D. That describes the recent direction of the two lines, and it says nothing about the next bar.
Fast, slow and full: the same formula with different smoothing
StockCharts sets out three forms with the same 14-period look-back and different smoothing. The table compares them.
- MetaTrader 5: the stochastic inputs are %K periods, %K slowing, %D periods and %D method. A slowing value of 1 is described as fast and 3 as slow. The method can be exponential, simple, smoothed or weighted.
- The MetaTrader 5 help page writes the %D formula as SMA(%K, N). Because the %D method input can be set to another type, check it before comparing its lines with another chart.
| Form | %K | %D | Default settings |
|---|---|---|---|
| Fast | Raw %K from the formula | 3-period average of fast %K | 14, 3 |
| Slow | 3-period average of fast %K | 3-period average of slow %K | 14, 3 |
| Full | Fast %K smoothed over the %K smoothing period | SMA of full %K over the %D period | 14, 3, 3 (look-back, %K smoothing, %D period) |
Source: StockCharts ChartSchool, Stochastic Oscillator Fast, Slow, and Full. The full form has three settings you choose: look-back (14), %K smoothing (3) and %D period (3), which are StockCharts defaults. Checked 10 November 2026.
Smoothing changes how closely the lines follow the raw %K readings. Which form suits a chart is a matter of testing your own settings, and any result describes the past.
The 80 and 20 levels and the 50 centreline
The conventional levels are 80 and 20. StockCharts describes 80 and 20 as the traditional overbought and oversold thresholds, and says the levels can be adjusted to suit analytical needs. It also uses 50 as a centreline. In this guide the labels describe where %K sits in its range. They are not signals that a price is about to turn.
- Because the scale runs from 0 to 100, a reading above 80 places the close in the upper fifth of the look-back range. This follows from the formula, not from a cited rule.
- Likewise, a reading below 20 places the close in the lower fifth of that range.
- Price can stay above 80 for a long time in a strong trend, and below 20 in a falling market. A level describes position, not timing.
Stochastic RSI: the stochastic formula applied to RSI
Stochastic RSI, often written StochRSI, applies the stochastic formula to a series of relative strength index (RSI) values instead of to closing prices. StockCharts credits Tushar Chande and Stanley Kroll with developing it. RSI is a separate momentum measure, and this guide does not explain it in full.
StockCharts gives the formula as (RSI minus lowest RSI) divided by (highest RSI minus lowest RSI), with a default look-back of 14 periods. The table sets the two versions side by side.
| Measure | Input series | Core formula | Default | Scale and levels |
|---|---|---|---|---|
| Stochastic oscillator (%K) | Closes with the high and low range | (C minus LL) divided by (HH minus LL) | 14, with 3 for smoothing and %D | 0 to 100, with 80 and 20 levels |
| Stochastic RSI | RSI values | (RSI minus lowest RSI) divided by (highest RSI minus lowest RSI) | 14 (StockCharts) | 0 to 1 on StockCharts, with 0.80, 0.20 and 0.50 levels |
Sources: StockCharts ChartSchool, StochRSI and Stochastic Oscillator Fast, Slow, and Full. Checked 10 November 2026.
The variant to check is the scale. StockCharts shows StochRSI from 0 to 1, so 0.80 and 0.20 match 80 and 20 on a 0 to 100 scale. Settings and scales vary between platforms, so confirm which one your chart uses before you compare readings with a written example.
Because StochRSI applies the range calculation to a series that is already a derived momentum value, its readings reflect RSI as well as price. That is a property of the arithmetic, not a forecast.
Reading %K and %D together
Charting texts describe %K crossing %D, lines moving above 80 or below 20, and divergence between the lines and price. A crossover shows that the fast line moved relative to its average. It does not show that the move will hold.
Crossovers in a sideways market can repeat several times, so one cross shows only a single recent change in the position of the two lines. The stochastic shares the high-low range idea with Williams %R. For a different design, see the Ultimate Oscillator.
Limits of the stochastic oscillator
- It describes where the close sits in a fixed look-back window. It does not predict the next move.
- It is bounded between 0 and 100, so it can stay at an extreme while price keeps trending.
- Settings change the readings. Changing the look-back, smoothing or %D method changes the lines and crossovers.
- Stochastic RSI adds another layer of calculation on top of RSI, with its own settings and scale.
- It uses past prices and no volume, so it cannot show how many shares or contracts traded at a level.
Before using any reading in a plan, check the settings and the scale on your own platform. To compare a stop and a target against a reading, see the risk-reward ratio.
Risk disclosure
- The stochastic oscillator and Stochastic RSI describe past prices. A reading does not show that a price will rise, fall or reverse.
- Settings, scale and smoothing change the lines. The same market can show different crossovers on two platforms, so check your own settings before you rely on a reading.
- Readings above 80 or below 20 can persist for a long time in a trend, so a level alone is not a timing tool.
- Crossovers in a range can repeat and produce false readings. Losses can occur on any trade, and leveraged products can lose money quickly; see margin in trading.
- This page is educational and is not personal financial advice. The examples use invented numbers and are not recommendations.
RTX5 status
This guide explains the stochastic oscillator in general and does not describe an RTX5 feature. No RTX5 release record confirms which indicators, chart types or alerts the product includes. Its Windows desktop client is in preview, and the web and mobile clients are planned. A Google Play listing for Android is published, but the mobile client has no approved release record yet; check the product-availability record before relying on any RTX5 feature.
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Primary references
Sources were checked on 10 November 2026. They explain market rules and concepts; they do not certify RTX5 or provide individual financial advice.
StockCharts ChartSchool: Stochastic Oscillator Fast, Slow, and FullGives the %K and %D formulas, the fast, slow and full forms with defaults 14, 3 and 14, 3, 3 (look-back, %K smoothing, %D period), the 80 and 20 levels, and the attribution to George Lane in the late 1950s. Checked 10 November 2026.StockCharts ChartSchool: StochRSIGives the StochRSI formula on RSI values, the default look-back of 14 periods, the attribution to Tushar Chande and Stanley Kroll, and the 0 to 1 scale with 0.80, 0.20 and 0.50 levels. Checked 10 November 2026.MetaTrader 5 help: Stochastic OscillatorLists the inputs %K periods, %K slowing (1 fast, 3 slow), %D periods and %D method, and writes the %D formula as SMA(%K, N). It does not print default values. Checked 10 November 2026.RTX5 product availabilityRTX5 status record. Use it to check which RTX5 products and clients are live before relying on any feature.
Questions readers ask
What is the stochastic oscillator?
The stochastic oscillator is a momentum indicator developed by George Lane. It compares the latest close with the highest high and lowest low over a look-back period, usually 14 periods, and scales the result from 0 to 100. In the standard form the %D line is a 3-period simple moving average of %K. It describes where price closed within its recent range, and it does not show the next move.
What is the difference between %K and %D?
In the fast form, %K is the raw reading: the position of the latest close within the look-back range, from 0 to 100. The slow and full forms smooth it first. %D is a moving average of %K, a 3-period simple average in the StockCharts default, so it moves more slowly. Traders describe crossovers between the two lines, but a crossover describes past readings and does not prove that a trend will continue.
What is the difference between fast, slow and full stochastic?
The fast form uses the raw %K and a 3-period average for %D. The slow form smooths %K with a 3-period average before taking %D, which makes the lines steadier. The full form lets you set the look-back, the %K smoothing and the %D period. StockCharts uses 14, 3 and 3 as defaults. Check your platform's settings, because defaults and labels differ between platforms.
What is stochastic RSI?
Stochastic RSI applies the stochastic formula to a series of RSI values instead of closing prices. Tushar Chande and Stanley Kroll are credited with developing it. StockCharts gives the formula as (RSI minus lowest RSI) divided by the RSI range, with a default look-back of 14 periods, and shows it on a 0 to 1 scale. Check the scale your platform uses before you compare readings.
Are the 80 and 20 levels buy or sell signals?
No. The 80 and 20 levels are conventional markers on the 0 to 100 scale, which places them at the upper and lower fifths of the look-back range. A reading above 80 places the close near the top of that range, and a reading below 20 places it near the bottom. Price can stay in either zone for a long time, so a level describes position rather than timing, and it is not advice.
Does the stochastic oscillator work?
This guide cannot say that it works. The indicator is arithmetic on past prices and makes no claim about future results. Its readings depend on the settings, the scale and the market, and they can produce repeated crossovers in a range. Test any use on your own data, and do not treat a stochastic reading as a reason to trade.
Keep learning
Williams %RA related range-based oscillator that uses the same high-low idea on a different scale.Ultimate OscillatorA separate oscillator with its own construction, for comparison with the stochastic.What is MACD?A momentum indicator built from two moving averages, for comparison with the stochastic.Risk-reward ratioHow to compare the distance to a stop and a target before using any reading.