Delta

What it is

Delta is the signed difference between buyer-initiated volume and seller-initiated volume over a defined period. Trades printing at the ask are buyer-initiated and count as positive; trades printing at the bid are seller-initiated and count as negative. Sum them across a bar and you get bar delta. Sum across a session and you get session delta. Watch them tick-by-tick and you get instantaneous delta.

Concretely: if 1,000 contracts trade at the ask and 600 trade at the bid during a one-minute bar, that bar has a delta of +400 — net aggressive buying. Negative delta means the period was dominated by sellers hitting bids. Zero delta means the two sides matched.

The reason delta exists as a metric is that raw volume alone is direction-blind. A 5,000-contract bar tells you the market was active, but not who was pushing. Delta puts a sign on that activity and turns volume into intent.

Why it matters

Delta tells you the balance of aggression — which side was paying up rather than waiting. That matters for two reasons:

• Continuation: if price is making new highs and delta is positive and rising, buyers are still paying up. The move has fuel.
• Exhaustion / absorption: if price is at new highs but delta keeps growing without further price progress, buyers are aggressing but the move has stalled — passive sellers are absorbing the flow. That's a high-information condition.

Delta is also one of the cleanest divergence signals available intraday. Price prints a higher high, delta prints a lower high — that's a textbook warning that the move lacks underlying participation.

How traders use it on Sierra Chart

Sierra Chart computes delta from its tick-level bid/ask volume data. It surfaces in several places: as a numerical column inside Numbers Bars footprint cells, as standalone delta studies plotted in a sub-pane, or as bar coloring overlaid on price. Cumulative session delta (CVD) is typically plotted as a separate study below price.

Most traders watch a combination — per-bar delta to see immediate aggression, CVD to see the running net, and footprint cells to see where in the bar delta was generated.

Common patterns / pitfalls

• High delta with little price movement = absorption. The aggressor is paying up but not getting paid in price terms.
• Delta divergence at session highs/lows is a high-quality reversal warning, especially when combined with a structural level.
• Delta in low-volume sessions (overnight, holidays) is noise — the sample size is too small to mean anything.
• Bid/ask classification quality depends entirely on the data feed. Reconstructed or end-of-day delta is unreliable.
• Don't confuse delta with imbalance. Delta is net flow over a bar; imbalance is a per-price-level ratio inside a footprint cell.

Related SCS studies

Delta Candle Color recolors price bars by the dominant side of aggression for each bar, making delta visible at a glance without a separate pane. CVD Filled Area plots the cumulative delta as a filled session-anchored curve, making divergences against price obvious.