Aggressor Ratio
Aggressor ratio is the proportion of buy-initiated volume to total volume over a given period, expressed as a percentage. A ratio above 50% indicates net buying aggression; below 50% indicates net selling aggression.
Aggressor ratio (also called buy ratio or buy/sell ratio) measures the percentage of total volume that was initiated by buyers versus sellers over a given period.
Aggressor Ratio = Buy Volume ÷ (Buy Volume + Sell Volume) × 100
A ratio of 60% means 60% of all volume was buy-initiated (lifted the ask) and 40% was sell-initiated (hit the bid).
Interpreting aggressor ratio
| Ratio | Interpretation |
|---|---|
| 70%+ | Strongly buy-dominated: aggressive buyers in control |
| 55–70% | Moderate buy dominance |
| 45–55% | Balanced: neither side dominant |
| 30–45% | Moderate sell dominance |
| Below 30% | Strongly sell-dominated: aggressive sellers in control |
These thresholds are approximate and context-dependent. During a strong trend, a sustained ratio of 65%+ in the trend direction is confirming. The same ratio during a choppy session may be noise.
Aggressor ratio vs cumulative delta
They measure related but different things:
- Cumulative delta: the absolute difference between buy and sell volume (in contracts)
- Aggressor ratio: the proportional split, normalized for total volume
Aggressor ratio is more comparable across different times of day or instruments because it accounts for varying volume levels. A delta of +500 contracts means more during lunch than at the open when total volume is 10× higher.
Practical use
Aggressor ratio is particularly useful for:
- Confirming whether a price move had genuine backing from aggressive flow
- Identifying exhaustion when ratio extremes (above 75% or below 25%) fail to produce continued price movement
- Session-level context: if the morning’s overall ratio is 62% buy, you are in a buyer-dominated session and should weight long setups higher