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Cumulative delta
Working definition
The running sum of buyer-aggressed minus seller-aggressed volume — one line tracking which side has been crossing the spread harder, accumulated trade by trade.
Volume answers how much; delta asks the sharper question — how much, and who insisted.
The construction inherits everything from the footprint chart’s machinery: classify each print by aggressor — at the ask, a buyer paid to cross; at the bid, a seller did; prints between the quotes take a stated rule — then sum sizes with sign. Rendered per bar it gives delta and its range; accumulated it gives the cumulative line this entry names. The classification is a convention, not a revelation, and every delta figure quietly carries its convention the way a profile carries its window: change the rule and identical prints draw a different line.
What the line uniquely shows is the gap between aggression and progress. Price and delta advancing together is the unremarkable case. The interesting prints are the disagreements — price pushing to new extremes while delta stalls, or delta pressing hard while price refuses to move. The vocabulary calls the first divergence and reads it as absorption: aggressive flow being met by resting size that declines to budge, the tape’s-eye view of the absorb/sweep balance the book measures directly. The reading is coherent and it is an inference — delta is built from the tape, and absorption is a claim about the book, so the line is always reasoning about a layer it cannot see. Its book-side sibling, order flow imbalance, watches that layer directly, which is why the two instruments disagree productively.
The FX caveat is structural, not a footnote. Delta was born where a consolidated tape makes “the market’s trades” a real object. Spot FX has no such tape, and much of it quotes without dependable per-trade sizes — so an FX delta is the signed sum of one feed’s business under one convention: a genuine measurement of that book, and a different line on a different feed. Quoting an FX delta without its feed is quoting a temperature without saying which room.
The divergence readings, like every reading in this family, are testable — outcomes after divergences against matched non-divergent extremes, per convention, per feed — and the two lenses keep the line’s arithmetic separate from the story told over it.
Commonly confused with
Neighbouring concepts that get used interchangeably, and the distinction that actually separates them.
- Volume
Volume counts everything that traded; delta signs it first. A heavy-volume bar with delta near zero and the same bar with delta deeply one-sided are different events wearing the same volume print — the signing is the information.
- Order flow imbalance
Order flow imbalance is built from the book — arrivals, cancellations and replenishment of resting orders; delta is built from the tape — executed trades signed by aggressor. Related instruments pointed at different layers: one watches intention change, the other counts consummated aggression.
- A footprint chart
The footprint keeps the per-bar, per-price ledger; delta sums that ledger into one running number. The compression is the point and the cost: delta answers "who has been more aggressive" while discarding where, at what prices, against what resting size.
- Sentiment
Delta measures executed aggression, not opinion. A market can lean bullish in every survey while delta runs negative for hours, because delta only counts those who paid the spread to act — and only on the feed being measured.
How to measure it in your own data
A definition you cannot test is a definition you have to take on trust. This is the shortest honest route from the concept to a number you computed yourself.
- Records you need
Per-trade prices and sizes with the bid/ask context to classify each print's aggressor — and the feed's identity, since in FX the tape being summed is one book's slice of the market.
- What you compute
Classify each trade by the stated convention — at the ask, buyer-aggressed; at the bid, seller-aggressed; a stated rule for prints between — then accumulate signed size. Per-bar delta, its high-low range, and the running cumulative line are the standard renderings; the convention is a parameter carried by all three.
- What the answer tells you
Price and delta agreeing reads as initiative; price advancing while delta stalls or drains — the divergence reading — is taken as absorption, aggression being met by resting size that does not move. The picture is checkable; the interpretation is an inference about the book made from the tape.
Questions and answers
What is cumulative delta in trading?
A running total of signed volume: each trade classified as buyer- or seller-aggressed by where it printed against the quotes, sizes summed with sign. The line answers one question — which side has been crossing the spread harder, cumulatively — on the feed being measured.
What is a delta divergence?
Price making a new extreme while cumulative delta declines to confirm it — new highs on fading buyer aggression, or new lows on fading seller aggression. The standard reading is absorption; the honest addition is that the reading is an inference, and its hit rate is a measurable proposition rather than a given.
Is cumulative delta accurate in forex?
It is exactly as accurate as its inputs: an aggressor classification that is a convention, applied to a tape that in spot FX is one feed's partial record, often without dependable per-trade sizes. The line is a real measurement of that feed. Treating it as the market's delta imports a consolidated tape FX does not have.
Why did delta stay positive while price fell?
Because aggression and progress are different quantities: buyers can keep crossing the spread into resting supply large enough to absorb them, and price grinds lower anyway. That disagreement is not the indicator failing — it is the one thing delta uniquely shows, whatever it turns out to predict.
Related terms
Derived from the links this entry makes and the entries that link back to it.