Implementation guide · Copy Trading and Allocation
Copy Trade Lot Multipliers and Exposure Limits
Apply a declared copy multiplier to a master quantity, then check contract units, existing exposure and limits before treating it as executable size.
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Published by FxTrusts, a supplier of brokerage and prop firm technology. Prepared with AI-assisted research and drafting; reviewed against the cited public sources. Examples are illustrative. Product links describe our services.
Quick answer
A fixed copy multiplier scales a source trade quantity by a stated factor. The result is only a target quantity. Contract equivalence, minimum steps, available margin and exposure limits must be checked before execution; the same multiplier does not create the same risk across different accounts.
Define the multiplier’s input
A multiplier can apply to lots, base-currency units or another quantity, depending on the system. State which source value is multiplied and whether the source and destination contracts are equivalent. Multiplying one forex lot into one differently sized CFD contract is not a valid one-to-one transformation. Keep the instrument mapping and contract-size conversion separate from the scaling factor so each can be verified independently.
Do not confuse fixed and equity-based sizing
A fixed factor of 1.5 remains 1.5 until changed under its policy. An equity-ratio copier can produce a changing factor as provider and follower values change. cTrader Copy documents a platform-specific equity model; it should not be described as a universal fixed-multiplier implementation. If a system combines a base ratio with an extra multiplier, both inputs and the order of operations need to be recorded.
Apply capacity checks to the resulting account state
A valid target can still exceed a per-order limit, aggregate exposure limit or available margin. Include current positions and relevant pending requests when checking the next state. The control should define whether it rejects the request or permits an explicitly authorized smaller quantity. Silently reducing size can break the intended relationship to the master, while blindly accepting it can violate the chosen account policy.
Treat multiplier changes as operational changes
Changing a factor may affect future trades only or may cause existing positions to be resized, depending on the implementation. That distinction needs a clear user-facing explanation and an acceptance test. Preserve the old and new settings, effective time and any resulting orders. A larger or smaller factor is not a recommendation about risk; price gaps, costs and differing account leverage can still produce outcomes that a simple quantity ratio does not capture.
A target quantity that exceeds a declared cap
Assume equivalent forex contracts, a master order of 0.40 lots and a fixed factor of 1.5. The target is 0.60 lots. The follower already has 0.30 lots in the same direction, while a fictional aggregate cap permits 0.80. The projected 0.90 exceeds that cap by 0.10. Under this example’s reject-on-excess policy, no new order is submitted; a smaller quantity would require a separately authorized policy.
| Input/check | Calculation | Result |
|---|---|---|
| Target quantity | 0.40 × 1.5 | 0.60 lots |
| Projected aggregate | 0.30 + 0.60 | 0.90 lots |
| Declared cap | 0.80 lots | Exceeded by 0.10 |
| Example action | Reject rather than silently resize | Record reason and requested quantity |
Implementation checklist
- Declare the quantity unit and confirm equivalent contracts.
- Separate fixed factors from equity-ratio inputs.
- Check the projected account state, including relevant pending requests.
- Document whether setting changes affect future trades or existing positions.
Sources
These documents support the reference. Check the original publication for current requirements and the limits of its scope.
- cTrader Copy documentationhelp.ctrader.com
- MQL5 symbol propertieswww.mql5.com
- Interactive Brokers default allocationswww.ibkrguides.com
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