Slippage, Partial Fills, and Realized Price
Measure execution from a defined reference and account for orders filled across prices and times.
Key takeaways
- Define the reference before measuring slippage.
- Calculate from every fill.
- Plan how to handle an unfilled remainder.
Slippage, Partial Fills, and Realized Price: the decision context
Slippage compares a specified reference with realized execution. Record the reference type, sign convention, and timestamp so the measure is reproducible.
Multiple fills require a volume-weighted average, while worst price and completion time add context. Venue exports are stronger evidence than a chart's last trade.
What evidence deserves attention
Partial fills leave unintended residual exposure and force choices about waiting, canceling, or repricing. Define that procedure before submission.
A repeatable review workflow
For fills of 2 units at 100 and 3 at 101, the realized average is 100.60. Against a 100.20 decision-time midpoint, buy slippage is 0.40 per unit before fees; retain timestamps and the unfilled quantity so the calculation is auditable.
Limits, failure modes, and risk
Depth, volatility, latency, size, and queue position all influence slippage. Segment actual records to calibrate estimates, while acknowledging future conditions can differ.
The chosen benchmark can flatter or penalize execution, especially when prices move during a long order. Missing fills, canceled remainders, hidden liquidity, clock skew, and selection of only completed orders can materially bias a slippage study.
Frequently asked questions
What is the first thing to distinguish in Slippage, Partial Fills, and Realized Price?
Start with this article's central checkpoint: Define the reference before measuring slippage. Then verify the definition and scope against the cited sources.
How can I check Slippage, Partial Fills, and Realized Price in practice?
Use the worked procedure in the article and keep these two checks together: Calculate from every fill. Plan how to handle an unfilled remainder.
What is the most important limitation?
Partial fills and slippage can leave unintended exposure or losses beyond the quoted price.
How this article was prepared
This educational article was prepared with AI assistance, then reviewed editorially for clarity and checked against the cited source material.