What is the Stochastic Oscillator?

What is the Stochastic Oscillator?

A stochastic oscillator is a momentum indicator comparing a particular closing price of a security to a range of its prices over a certain period of time. The sensitivity of the oscillator to market movements is reducible by adjusting that time period or by taking a moving average of the result.

It is used to generate overbought and oversold trading signals, utilizing a 0–100 bounded range of values.

Stochastic Oscillator Formula

The formula for calculating the Stochastic Oscillator is as follows:

%k = (Last Closing Price – Lowest Price)/(Highest Price – Lowest Price) x 100

%D = 3-day SMA of %K


  • C is the last closing price
  • Lowest Low is the lowest low for the time period
  • Highest High is the highest high for the time period

What Does the Stochastic Oscillator Tell You?

The stochastic oscillator is range-bound, meaning it is always between 0 and 100. This makes it a useful indicator of overbought and oversold conditions. Traditionally, readings over 80 are considered in the overbought range, and readings under 20 are considered oversold.

However, these are not always indicative of impending reversal; very strong trends can maintain overbought or oversold conditions for an extended period. Instead, traders should look to changes in the stochastic oscillator for clues about future trend shifts.

Stochastic oscillator charting generally consists of two lines: one reflecting the actual value of the oscillator for each session, and one reflecting its three-day simple moving average. Because price is thought to follow momentum, the intersection of these two lines is considered to be a signal that a reversal may be in the works, as it indicates a large shift in momentum from day to day.

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Uses of the Stochastic Oscillator

The following are the primary uses of the stochastic oscillator:

1. Identify overbought and oversold levels

An overbought level is indicated when the stochastic reading is above 80. Readings below 20 indicate oversold conditions in the market. A sell signal is generated when the oscillator reading goes above the 80 level and then returns to readings below 80.

Conversely, a buy signal is indicated when the oscillator moves below 20 and then back above 20. Overbought and oversold levels mean that the security’s price is near the top or bottom, respectively, of its trading range for the specified time period.

2. Divergence

Divergence occurs when the security price is making a new high or low that is not reflected on the Stochastic Oscillator. For example, price moves to a new high but the oscillator does not correspondingly move to a new high reading.

 This is an example of bearish divergence, which may signal an impending market reversal from an uptrend to a downtrend. The failure of the oscillator to reach a new high along price action doing so indicates that the momentum of the uptrend is starting to wane.

Similarly, a bullish divergence occurs when the market price makes a new low but the oscillator does not follow suit by moving to a new low reading. Bullish divergence indicates a possible upcoming market reversal to the upside.

It’s important to note that the Stochastic Oscillator may give a divergence signal some time before price action changes direction. For instance, when the oscillator gives a signal of bearish divergence, price may continue moving higher for several trading sessions before turning to the downside.

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This is the reason that Lane recommends waiting for some confirmation of a market reversal before entering a trading position. Trades should not be based on divergence alone.

3. Crossovers

Crossovers refer to the point at which the fast stochastic line and the slow stochastic line intersect. The fast stochastic line is the 0%K line, and the slow stochastic line is the %D line. When the %K line intersects the %D line and goes above it, this is a bullish scenario. Conversely, the %K line crossing from above to below the %D stochastic line gives a bearish sell signal.

Limitations of the Stochastic Oscillator

The main shortcoming of the oscillator is its tendency to generate false signals. They are especially common during turbulent, highly volatile trading conditions. This is why the importance of confirming trading signals from the Stochastic Oscillator with indications from other technical indicators is stressed.

Traders need to always keep in mind that the oscillator is primarily designed to measure the strength or weakness – not the trend or direction – of price action movement in a market.

Some traders aim to lessen the Stochastic Oscillator’s tendency to generate false trading signals by using more extreme readings of the oscillator to indicate overbought/oversold conditions in a market. Rather than using readings above 80 as the demarcation line, they instead only interpret readings above 85 as indicating overbought conditions. On the bearish side, only readings of 15 and below are interpreted as signaling oversold conditions.

Example of How to Use the Stochastic Oscillator

The stochastic oscillator is included in most charting tools and can be easily employed in practice. The standard time period used is 14 days, though this can be adjusted to meet specific analytical needs. The stochastic oscillator is calculated by subtracting the low for the period from the current closing price, dividing by the total range for the period and multiplying by 100.

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 As a hypothetical example, if the 14-day high is $150, the low is $125 and the current close is $145, then the reading for the current session would be: (145-125) / (150 – 125) * 100, or 80.

By comparing the current price to the range over time, the stochastic oscillator reflects the consistency with which the price closes near its recent high or low. A reading of 80 would indicate that the asset is on the verge of being overbought.