Lesson 1 of 1 · 2 min
Delta
Aggressive buying minus aggressive selling — per bar, per price, and cumulatively. Useful, and very easy to misread.
Delta compares aggressive buying with aggressive selling. It's the single number most orderflow tools are built around — and the one most often over-interpreted.
Definition
Delta = volume traded at the ask − volume traded at the bid, over a bar, a price, or a period. Cumulative delta (CVD) keeps a running total across the session.
What delta tells you
- Which side was more aggressive — more willing to cross the spread — during the window.
- Whether aggression and price are moving together or diverging.
What it does not tell you
- Who was buying or selling more overall — every contract has both a buyer and a seller.
- Who is right. Passive participants on the other side of aggression often win.
- Anything precise when classification is uncertain (see Footprint → Trade Classification).
Key Insight
The interesting cases are divergences: strong positive delta while price fails to rise suggests passive selling absorbing the buyers. Strong negative delta while price holds suggests the opposite.
Cumulative delta
CVD is useful for comparing swings — does a new high come with more or less aggressive buying than the last one? It depends heavily on its start point and on the feed's classification, so read its shape, not its absolute value.
Trading implication
Read delta relative to price movement and only at locations you care about. Delta on its own, out of context, is close to noise.
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