Leader–Follower Copy Sizing Multipliers for Futures Accounts

If the leader fills four contracts and a follower has a 0.50 multiplier, the raw follower quantity is two. If the multiplier is 1.25, the raw quantity is five. The arithmetic is simple; the operating policy around it is not. Futures orders require whole contracts, accounts have different drawdown room, and the same contract can represent too much risk for a smaller follower.

Use the multiplier as one layer in a sizing pipeline rather than as an instruction to blindly reproduce the leader. The pipeline should identify the filled leader increment, apply the follower's configured ratio, use a declared rounding rule, clamp the result to symbol and account caps, and skip the order if any eligibility gate fails. The displayed preview should show both the raw calculation and final requested quantity.

Sizing does not determine execution. A calculated follower request can still be rejected or partially filled, and a successful fill can occur at another price. Keep target quantity, requested quantity, and broker-reported filled quantity as separate fields so risk and drift remain measurable.

For an incremental fill model, let L be the newly reported leader fill quantity and M be the follower multiplier. The raw copy quantity is L × M. Apply the configured rounding method to that number, then take the lower of the rounded quantity, the account maximum, and the symbol maximum. If the account is paused, disconnected, outside policy, or below one contract after rounding, the final quantity should be zero with a visible skip reason.

Incremental fills require extra care with fractions. Imagine two separate one-contract leader fills and a 0.50 follower multiplier. Rounding each increment down produces zero plus zero, although the cumulative target is one. A stateful design can carry the fractional remainder: the first fill creates a 0.5 remainder and no order; the second brings the cumulative target to one. Whatever model is used, document it so operators can predict behavior.

Start with the follower's maximum planned loss for one trade, not with its buying power. Estimate per-contract risk from stop distance × tick value, then add commissions and a slippage reserve. Divide the follower loss budget by that conservative per-contract estimate and round down to obtain a risk-based contract cap. The multiplier should not create a final quantity above that cap.

For example, if a follower permits a $120 planned loss and the estimated all-in risk is $42 per MES contract, its risk-based maximum is two contracts, not 2.85. If the leader commonly trades four MES, a starting multiplier of 0.50 expresses that cap. Recalculate when the strategy's stop behavior, volatility, fees, contract month, or account drawdown state changes.

The leader's quantity may itself vary. A fixed follower quantity can be useful when you want a stable exposure independent of the leader, while a multiplier preserves proportional changes. Do not mix those policies silently. Label the sizing mode and show the resulting quantity before activation.

A multiplier has no risk meaning without the contract. One ES contract and one MES contract do not have equal economic exposure. A follower mapping that changes the contract family needs an explicit conversion based on current specifications, not a reused account-size ratio. Likewise, an expiry mapping error can send an order to an unintended or illiquid contract.

Maintain a small symbol record with the platform symbol, root, expiry, tick size, tick value, and intended conversion. Review it around rollover and whenever a connector changes. CME contract specifications are the primary reference for listed contract economics; the platform's documentation governs the exact order symbol accepted by its API.

If the group intentionally maps a larger leader contract to micro followers, test both directions and several leader quantities. A conversion that works for one contract may create large rounding jumps. Put a hard cap after conversion so an incorrect mapping cannot fan out an unexpectedly large order.

Flooring is conservative for a single calculation but can systematically under-copy a stream of small partial fills unless fractions are accumulated. Rounding to nearest can create a one-contract follower order from a raw target below one, which may exceed the intended ratio on a small account. Ceiling is usually the most aggressive and should never appear as an undocumented default.

Caps protect against configuration errors and changing conditions. Use at least an account-level maximum, a per-symbol maximum, and a group aggregate warning. The account cap limits a single follower request; the aggregate warning helps the operator see that one leader action may create substantial correlated exposure across many accounts.

Every zero should have a reason such as rounded below minimum, follower paused, risk cap reached, unsupported symbol, or connection unavailable. A silent zero looks like a system failure, while an unexplained nonzero can become a risk incident.

The cumulative target is more useful than checking whether each individual copy request matched. It accounts for fractional carry, partial fills, exits, and reversals. Store a signed target position for the follower and compare it with the latest broker-reported signed position. The difference is quantity drift; fill-price variation is a separate measure.

A one-contract difference may be expected while a partial order is working, or it may indicate a rejection that needs action. Attach state and age to the drift. “One contract under target for 300 milliseconds with a live order” is different from “one contract under target for three minutes after a reject.” Alert on actionable persistence rather than any instantaneous mismatch.

Do not automatically chase every mismatch without limits. A correction submitted into a fast market can fill after another event has changed the target. Pause, refresh order and position state, calculate one current correction, and track that order like any other follower outcome.

Write down the expected result for leader quantities one through five before the test. Include partial-fill sequences and the exact rounding behavior. This catches surprising discontinuities while the group is still paused. Then use a micro contract and the smallest follower set that can validate the intended connector path.

During the test, compare the leader fill increment, raw follower target, final requested quantity, broker acknowledgement, filled quantity, and final position. Test a normal exit and a rejected or deliberately ineligible case so the skip and alert paths are visible. Never manufacture a live rejection by violating a broker rule; use a safe configuration gate or simulation environment where available.

After a clean cycle, add followers in batches and recalculate aggregate exposure. Keep a rollback action: pause the group, leave existing positions unchanged, or flatten under a separately confirmed procedure. Review multipliers whenever account equity, drawdown room, strategy stops, contract choice, or firm policy changes.