Measuring slippage in copy trading

A price difference between provider and follower is often the first execution issue noticed in copy trading. Yet a number without an agreed benchmark and order side is not a reliable measure. Timing, different markets and partial fills may contribute. Start by stating exactly which gap is being measured.

Choose the benchmark before inspecting results

The reference might be the provider’s execution price or an executable quote when the follower receives the instruction. The former captures the gap between two executions; the latter examines a different segment of the process. A chart midpoint is not necessarily an executable buy or sell quote. Changing the reference after seeing results biases comparison, so retain both the reference and its source.

The sign depends on the order side

If positive means adverse price cost, a buy can use follower fill minus reference; a sell can use reference minus follower fill. A negative value under this convention means a better price relative to that reference. Use the actual order side: closing a long position is a sell, while closing a short is a buy.

Two hypothetical examples with explicit units

For a EUR/USD buy with a 1.1000 reference and a 1.1002 fill, the adverse difference is 0.0002, or two pips when a pip is 0.0001. A sell with the same reference and a 1.0998 fill also has two adverse pips. This measures a price gap, not total account costs. Converting it into money requires position size and contract specifications.

Combine partial fills carefully

When one instruction fills in several portions, weight each price by its executed quantity rather than taking a simple price average. Keep the unfilled quantity and its status separately. Reviewing only successful portions does not describe the entire instruction. Record entry and exit as separate events too: a favourable entry does not guarantee a favourable exit.

Build a reconciliation table

• Matching identifiers, instruments and contract specifications for both accounts.
• Order side, requested quantity and the size of each fill.
• Submission, receipt and execution times, with timezone and clock precision.
• The reference price, its source and weighting method.
• Rejections, delays, partial fills and separately posted charges.

Do not stop at an average

Review observation counts, the range of differences and unusually adverse cases. Separate instruments, sizes and market hours; an unexplained mixture can conceal important variation. Rejected instructions have no actual fill price, so do not record their slippage as zero. Rejection rates and missed opportunities need separate reporting with clear limits on any estimate.

Measurement is not causal attribution

Unsynchronised clocks or different host quotes prevent assigning every difference to a particular software component. A gap between executions does not by itself prove misconduct, deliberate delay or a manager’s overall quality. Avoid counting a cost already reflected in the price benchmark a second time under the same label. Report commissions and holding charges with separate definitions.

When reviewing trading-account information, request reconcilable execution samples rather than relying only on a signal’s return percentage. The help centre can clarify terminology. This article is not a live platform execution report, a trading recommendation or a guarantee of copying quality.