Trade copier lot sizing: six modes, six different risks

A trade copier will open the same trade on a 2,000 account that a sender opened on a 100,000 account. Whether it opens it at the right size is a separate question, and the answer depends on a single setting. Get it wrong and the receiver does not copy the strategy. It copies the strategy at several times the risk.

Sender, Receivers and where the lot is decided

In the Social Trade Hub Trade Copier, the Sender is the source account and Receivers are the accounts that execute its trades. One Sender can feed any number of Receivers, and each Receiver carries its own risk configuration. That separation matters: a prop firm challenge account, a personal account and a small test account can all follow the same Sender while sizing trades in completely different ways.

Each Receiver uses one of six lot-sizing modes. In the app they are labelled Fixed lots, Lot per symbol, Copy sender lots, Risk by balance, Risk by equity and Risk in %. A new Receiver starts in Fixed lots at 0.01 lot. That is cautious, and rarely what anyone means to run long term.

The six modes fall into three families. Two ignore the sender's lot size, three scale it, and one sizes from the receiver's balance and the trade's stop loss. Knowing which family a Receiver is in tells you most of what can go wrong with it.

Fixed lots and Lot per symbol: ignoring the sender's size

Fixed lots does exactly what the name says. Every copied trade uses the same lot size, whatever the sender traded. If the sender opens 0.05 lots or 2 lots, the receiver opens the value you set. This is the most predictable mode there is, which is why it suits a first test of a new sender.

The cost is that the sender's sizing information is thrown away. If the sender sizes up on trades it rates highly, or down when its stop is wide, the receiver does not follow. And because the lot ignores the stop distance, the money at risk on the receiver changes from trade to trade.

Lot per symbol applies the same idea instrument by instrument: a fixed lot is set for each symbol individually. It helps when the sender trades instruments whose exposure per lot differs widely. The catch is the fallback. A symbol with no value in the list is copied at 0.01 lot, so if the sender starts trading an instrument you did not list, the receiver takes it at that size without warning. The list needs maintaining.

Copy sender lots: the mode that over-leverages small accounts

Copy sender lots takes the sender's lot size and multiplies it by a factor. With a multiplier of 2, a 0.1 lot trade becomes 0.2 lots. With a multiplier of 1, the receiver mirrors the sender exactly.

Account size never enters the calculation. Take a sender with a 100,000 balance that opens 1 lot, and a receiver with a 5,000 balance on a multiplier of 1. The receiver also opens 1 lot, which relative to its balance is twenty times the exposure the sender took. Nothing errors and nothing is flagged. The trades are simply too big, and the account finds out on the first losing run.

The mode fits accounts of similar size, or a receiver whose multiplier you have worked out by hand: 5,000 divided by 100,000 gives 0.05. But that multiplier is frozen. As the balances drift apart through deposits, withdrawals, profits and losses, the proportion stops being right and nothing corrects it. The next two modes do that correction for you.

Risk by balance and Risk by equity: scaling by the ratio

Risk by balance computes lots as sender lots multiplied by the ratio of receiver balance to sender balance, then by a multiplier. With the same two accounts, a 1 lot sender trade and a multiplier of 1 give the receiver 0.05 lots. If the receiver grows to 6,000, the next trade comes through at 0.06 without anyone touching the settings. The multiplier is still there if you want the receiver to run more or less aggressively than the sender in proportional terms.

Risk by equity uses the same ratio computed on equity instead. The difference is in the definitions. In the app, balance means account funds excluding bonuses and open trades. Equity means balance plus bonuses plus the profit or loss of open trades.

Balance is the stable figure. It moves when trades close or money moves in or out, so the ratio between two accounts stays the same regardless of what is open on either. Equity moves continuously with floating results on both sides. If the sender is sitting in a large floating loss when a new trade arrives, its equity is lower, the ratio is higher, and the receiver opens a bigger position than it would on balance. When the receiver is the one in drawdown, the effect reverses and its lots shrink. Bonuses count as well: a receiver holding bonus credit is sized as though that credit were its own money.

Equity gives sizing that reacts to open drawdown, but the same signal can then produce different lots depending on what is open at that moment. If you cannot say why you want that, balance is easier to reason about and easier to audit afterwards.

Risk in %: sizing from the stop loss

Risk in % takes a different approach. The receiver risks a set percentage of its balance per trade, and the lot is sized from the stop loss distance and the symbol's specifications at the receiver's broker. The sender's lot size plays no part. Two sender trades with different stops produce different lots on the receiver, but the same amount of money at risk if either stop is hit.

The lot is rounded down so the stated risk is not exceeded, so the actual risk on any trade sits at or slightly below the figure you entered.

For accounts with a hard loss limit, such as prop firm challenges, this is usually the mode that maps most directly onto the rule you are trying to respect. It is also the mode with the most ways of declining a trade, and those need to be understood before it goes live.

When Risk in % refuses to copy

Risk in % needs a stop loss, because without one there is no distance to size from. A trade copied without a stop loss is not opened, and the receiver log shows: 'You cannot copy a trade with a Stop Loss (SL) set to 0 while using the risk in percentage setting.' Senders that place their stop a few seconds after entry, or never place one, will trigger this.

The 'Apply default TP/SL in pips' option can supply a stop loss per symbol when the sender has none. That solves the refusal, with a trade-off: the copied trade now carries a stop the sender never set. The receiver can be stopped out of a trade the sender is still holding, and from that point the two accounts' results diverge.

The second refusal concerns wide stops. If the stop loss is so wide that even the broker's minimum lot would exceed the chosen risk, the trade is not copied and the log says the stop loss distance is too large for the balance and risk settings. Small balances, low percentages and wide stops make this more likely, and it can mean a receiver silently skips a whole category of the sender's trades.

Limits that apply in every mode

'Max lots' caps the lot size of every copied trade, whatever the mode. The default is 5. The final lot is also rounded to the receiver broker's lot step, so on very small receivers the lot actually opened can differ from the exact result of the formula.

A cap of 5 lots is a sanity limit for a large account, not protection for a small one. Set Max lots to the largest trade you would accept on that specific account. It is the backstop for a mistyped multiplier, an equity ratio that jumps, or an unusually large sender position.

The 'Minimum Balance' setting sits on the Sender rather than the Receiver. It stops new trades from being sent to any Receiver whose balance is at or below the threshold, so it acts as one floor for every Receiver at once. It governs new trades being sent. Positions already open on a receiver are a separate matter you still need to manage.

Choosing a mode for the situation

• Testing a new sender on a spare account: Fixed lots at a small size, with no sizing logic in the way.
• Receiver and sender of similar size: Copy sender lots, with the multiplier set deliberately.
• Receiver much smaller or larger than the sender: Risk by balance, so the proportion follows both balances over time.
• Sizing that should react to floating results: Risk by equity, accepting that the same signal can produce different lots.
• A hard loss limit to respect: Risk in %, with a default stop loss configured and a conscious decision about 'Force minimum lot if apply'.
• Instruments with very different exposure per lot: Lot per symbol, with the list kept current.

Receivers on the same Sender do not have to agree. A challenge account on Risk in % and a personal account on Risk by balance can follow the same trades side by side, each with its own Max lots.

What lot sizing cannot fix

No lot-sizing mode changes the quality of the sender's trades. The mode only decides how much of each trade the receiver takes. A sender with poor risk control is copied faithfully at whatever size you choose. Risk in % limits the loss on a single trade but does nothing about a long sequence of them, and the ratio modes pass the sender's own over-sizing straight through in proportion. Pick the mode that fits the account, then judge the sender separately, on its record, before deciding how much of its risk the account should carry.