KDJ K, D and J Lines Explained:
Formulas and Meaning
Learn the formulas for the K, D and J lines that make up the KDJ indicator, verified against multiple technical analysis sources.
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This lesson explains the three components of KDJ — the K line, D line, and J line — including the underlying RSV calculation they're built from.
These formulas have been verified against multiple technical analysis education sources for consistency.
The Starting Point: RSV (Raw Stochastic Value)
KDJ begins with RSV, calculated as: RSV = [(Close − Lowest Low over N periods) ÷ (Highest High over N periods − Lowest Low over N periods)] × 100. The standard period (N) is 9. RSV expresses where the current close sits within the recent high-low range, on a scale from 0 to 100 — a reading near 100 means the close is near the period's high, and a reading near 0 means it's near the period's low.
The K Line
The K line (the "fast line") is calculated as: K = (2/3) × Previous K value + (1/3) × Today's RSV. This is a smoothed value derived from RSV, generally responding relatively quickly to recent price changes. For the very first calculation, where no previous K value exists, a starting value of 50 is generally used.
The D Line
The D line (the "slow line") is calculated as: D = (2/3) × Previous D value + (1/3) × Today's K value. This applies the same smoothing process to K that K applied to RSV, making D slower-moving and less reactive than K, similar in concept to how a signal line smooths the MACD line (covered in the previous unit).
The J Line
The J line is calculated as: J = 3 × K − 2 × D. Unlike K and D, which are both bounded within 0–100, the J line's formula allows it to extend beyond this range in either direction, amplifying the divergence between K and D to provide a more exaggerated, sensitive reading. This J line is the specific addition that distinguishes KDJ from the traditional Stochastic Oscillator, covered in detail in this unit's final lesson.
🔖 Summary
KDJ is built from RSV (measuring where the close sits within its recent high-low range), smoothed into the K line (fast), further smoothed into the D line (slow), with the J line (3K − 2D) amplifying the divergence between K and D and extending beyond the standard 0–100 range that bounds K and D. This J line is the specific feature that distinguishes KDJ from the traditional Stochastic Oscillator.
Frequently Asked Questions
What is RSV in the KDJ calculation?
Raw Stochastic Value, calculated as [(Close − Lowest Low) ÷ (Highest High − Lowest Low)] × 100 over a standard period of 9, expressing where the close sits within the recent range.
What is the K line formula?
K = (2/3) × Previous K value + (1/3) × Today's RSV, a smoothed value derived from RSV.
What is the D line formula?
D = (2/3) × Previous D value + (1/3) × Today's K value, a further-smoothed, slower-moving version of K.
What is the J line formula, and how is it different from K and D?
J = 3K − 2D; unlike K and D, which are bounded 0–100, J can extend beyond this range, amplifying the divergence between K and D for a more sensitive reading.
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