Stochastic Oscillator
A momentum indicator that measures where the closing price sits within a recent high-low range, flagging overbought and oversold conditions.
Definition
The Stochastic Oscillator is a bounded momentum indicator developed by George Lane that compares a security's closing price to its price range over a specified lookback period, typically 14 periods. It produces two lines — %K (the fast line) and %D (a smoothed signal line) — both oscillating between 0 and 100. Readings above 80 are considered overbought and readings below 20 are considered oversold, though in strong trends price can remain in these zones for extended periods.
Why it matters
In Indian equity and derivatives markets, the Stochastic Oscillator is commonly used by intraday and swing traders to time entries after a stock or index has stretched too far in one direction. On NSE-listed stocks, a %K crossing above %D from below the 20 level can signal a short-term bullish reversal, while a cross below %D from above 80 can signal a sell-off. Traders also watch for divergence — where price makes a new high but the Stochastic makes a lower high — as an early warning that momentum is fading. The Stochastic tends to work better in sideways, range-bound markets; in strong trending markets it can generate premature signals and is best used in combination with a trend filter.
Formula
%K = [(Close − Lowest Low over N periods) ÷ (Highest High over N periods − Lowest Low over N periods)] × 100
%D = 3-period simple moving average of %K
The standard setting is N = 14 periods for %K, with %D as the 3-period smoothing. A "slow stochastic" applies additional smoothing to %K before computing %D, reducing noise and giving fewer but more reliable signals.
Example
Suppose a hypothetical NSE stock has a 14-day highest high of INR 1,200 and a lowest low of INR 1,050, with the most recent close at INR 1,065. %K = [(1,065 − 1,050) ÷ (1,200 − 1,050)] × 100 = (15 ÷ 150) × 100 = 10. A reading of 10 is deep in oversold territory. If on the next session %K turns up and crosses above %D while both remain below 20, a trader might consider buying a call option near the current price, with a stop below the recent swing low at 1,050. These figures are hypothetical only.
Combine momentum signals with options data
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