How lot sizes are calculated when copying trades between accounts

The four lot rules

The balance ratio keeps the risk per balance the same on both accounts. The equity ratio uses equity, which includes floating profit and loss, so the copy size follows it. A multiplier or a fixed lot ignores the accounts’ sizes: use them when you decide the risk yourself.

Leverage is not part of the calculation. It only decides how much margin a position needs, not how much it can win or lose per pip, so the lot-to-equity ratio is what sets the risk. Margin is covered below.

Rounding, minimum and maximum

• Rounded down to the broker’s volume step. 0.185 lot becomes 0.18 on a 0.01 step.
• Maximum lot. The size is capped at the broker’s maximum for the symbol, and at the maximum you set for the follower.
• Minimum lot. If the result is below the minimum, you choose: open at the minimum, or skip the trade. A skipped trade is shown in the copy log with the reason.
• Partial closes. When the master closes part of a position, the follower closes the same share of its own copy: 0.4 of 1.00 lot closed by the master means 0.10 of a 0.25 lot copy. If what would be left is below the broker’s minimum lot, the whole copy is closed.

Different contract sizes

A lot is not the same amount everywhere. One broker’s gold contract is 100 ounces, another’s is 10. Copying 0.5 lot of the first as 0.5 lot of the second would trade a tenth of the exposure.

So the copier compares the contract sizes first: 0.5 lot of a 100-ounce XAUUSD becomes 5 lots of a 10-ounce GOLD. The result then goes through the rule above. A fixed lot is the exception: it is used as you set it.

Different currencies and cent accounts

Balances are compared in the follower’s currency, converted with the follower broker’s own rates, so a EUR master and a USD follower end up with a sensible ratio. If no rate is available the trade is skipped, and the log says so.

Cent accounts (USC and EUC) are supported. Brokers build them in two ways: a smaller contract size, or a standard contract with the profit booked in cents. The copier works out which one an account uses from its contract sizes, so the lot comes out right for both.

Margin protection

A master with 1:2000 leverage can open a position that a 1:30 follower cannot afford with the same ratio, and the broker rejects it for lack of funds. The margin guard is a link setting with three values:

• Off (default): the order is sent as calculated and the broker decides.
• Reduce: if the trade would need more than 90% of the follower’s free margin, the lot is cut down to fit. If it would fall below the minimum lot, the trade is skipped.
• Skip: a trade that does not fit is left out.

Martingale and grid strategies

A master that raises its lot in a series (0.02, then 0.04, then 0.08) should have a follower that does the same. With series sizing switched on, the first trade of a series is sized by the normal rule, and the later trades in the same direction on the same symbol keep the ratio to it:

Here the follower’s rule gave less than its minimum for the first trade, so the minimum of 0.01 was used, and the ratio of 0.5 then held for the rest. Once every copy of the series is closed, the next trade starts a new series.

Check it before you copy

The link settings show a sample calculation: pick a master lot and see what the follower would get, with the formula, the ratio and any minimum or maximum that applied. Try the sizes your master really trades before the first live copy.

Questions