Position Sizing When Copying Trades: Equity-Ratio vs Fixed Lot

To copy trades between accounts of different sizes, scale the lot for each follower account rather than repeating the source lot as it is: by a fixed multiplier, or by the ratio of the two accounts' equity, which keeps every follower in proportion to its own size. Repeating 1.0 lot onto a follower with a tenth of the balance would over-expose it badly. This is arithmetic, not advice. It tells you the proportional lot for the inputs you give, nothing about what you should risk.

A worked example: two accounts, three sizing rules

A 2.00-lot trade on a $100,000 source account becomes 0.50 lots on a $25,000 follower under equity ratio, 1.00 under a fixed 0.5× multiplier, and 2.00 if the follower copies the same lot (a 1× multiplier, which is where a new Trepeat repeater starts).

The follower has a quarter of the source's equity, so the same lot is four times the exposure for its size, and 0.5× still doubles it. Only equity ratio lands at the same proportion, and it keeps doing so as the accounts change: if the follower's equity falls to $20,000 while the source stays at $100,000, the next 2.00-lot trade copies at 0.40, while both multipliers keep placing the same lots. The table assumes a 0.01 lot step, the same deposit currency and the same lot definition at both brokers. Run your own figures on the lot size calculator in copy-sizing mode, or switch it to a fixed multiplier.

What is a fixed multiplier when copying trades?

A fixed multiplier makes every follower trade the source lot times one constant, whatever its balance: at 0.5× a 1.0-lot source becomes 0.50, at 2× it becomes 2.00. It is predictable, but it ignores account size, so the same multiplier can be too big on a small follower and too small on a large one.

In Trepeat this is the sizing mode a new repeater starts in, at 1×. The multiplier can be set from 0.01× to 100×.

How does proportional sizing work when account sizes are different?

Proportional sizing, called equity ratio in Trepeat, multiplies the source lot by the follower's equity divided by the source's equity, so a follower five times the size of the source takes five times the lot.

follower lot = source lot × (follower equity ÷ source equity)

So a 1.0-lot trade on a $50,000 source becomes 2.00 lots on a $100,000 follower and 0.50 on a $25,000 one: each account takes proportionally the same exposure from a single rule. When account sizes differ, this keeps every follower in step without per-account tuning. The ratio is worked out again for each trade, from the latest equity Trepeat holds for the two accounts.

Five follower sizes, and what rounding does to them

A 0.30-lot trade on a $10,000 source becomes 1.50 lots on a $50,000 follower under equity ratio, and 0.15 lots under a fixed 0.5× multiplier. The table runs that same source trade across five follower sizes.

The source is 0.30 lots at $10,000 equity. The table assumes the follower symbol steps in 0.01 lots with a 0.01 minimum, both accounts use the same deposit currency, both brokers define a lot the same way, and no volume cap is set. Rounding is Floor, the setting a new repeater starts with.

Two rows show what rounding does. The $3,500 follower works out at 0.105 lots, which Floor takes down to 0.10; Round or Ceiling would place 0.11. The $250 follower works out at 0.0075 lots, below the 0.01 minimum: with Floor the copy is skipped, and with Round or Ceiling it becomes 0.01, a third more than its proportion.

Rounding, minimum lot, and a volume cap

After scaling, the lot is rounded to the step the follower's broker accepts for that symbol, capped if you set a cap, and skipped if what is left is below that symbol's minimum. Brokers only accept lots in steps (commonly 0.01), so the scaled figure has to be rounded, and how it rounds changes the exposure slightly:

• Floor rounds down, so a follower never exceeds the intended exposure (the safe default).
• Round goes to the nearest step, closest to intended on average.
• Ceiling rounds up, so the follower gets at least the intended size, unless a Max Volume cap or the broker's own maximum reduces it afterwards. It never more than doubles a copy: on a symbol that steps in 0.01 lots, 0.001 would need 0.01, ten times the size you meant, so that copy is skipped like one below the minimum.

Two edges matter. If the scaled lot rounds below the broker minimum (e.g. a tiny follower scaling to under 0.01), there's no valid order to place, so a faithful copier skips that copy rather than sending something invalid. And a maximum-volume cap lets you bound the per-order size a follower can take, applied after scaling, useful when a big source trade would otherwise scale a large follower past where you're comfortable.

In Trepeat a skipped copy stays on the Trades page with its reason, and an alert names the symbol and the follower. The cap is per order, not a limit on the total a follower holds: three copies of 1 lot each can add up to 3 lots on one symbol under a 1-lot cap.

The step matters most on instruments that do not step in 0.01. Some index and crypto CFDs step in 0.1, 1.0 or more. Scale an index position to 0.4 lots on a symbol whose step is 1.0, and the copy is skipped whichever rounding you choose: Floor and Round leave nothing to place, and Ceiling would need 1.0, two and a half times the proportion. At 0.6 lots, Round and Ceiling place 1.0.

Different lot definitions and deposit currencies

Two differences between the accounts change the copied lot before any rounding: how each broker defines a lot, and the currency each account is held in.

• Contract size. A lot is a number of units of the instrument, and brokers disagree: one lot of silver is 1,000 ounces at some brokers and 5,000 at others. Trepeat converts by source contract size ÷ follower contract size, so 1.00 lot on a 1,000-ounce source becomes 0.20 on a 5,000-ounce follower, which is the same exposure. There is no setting for this. Where a contract size is not known on either side, no conversion is applied.
• Deposit currency. Equity ratio divides one account's equity by the other's, which is only a ratio when both are in the same currency. When the two deposit currencies are known and differ, Trepeat sizes the copy with the repeater's saved multiplier instead. It does not convert one currency into the other.
• Missing equity. The same fallback to the multiplier applies when Trepeat holds no equity figure for one of the accounts. A source equity of zero or less skips the copy.

The full order these rules run in, from the symbol allowlist to the minimum check, is in repeater settings.

Try the numbers

The lot size calculator runs both sizing rules on your own figures in its "Copy sizing" mode: scale a source lot across accounts by equity-ratio or a fixed multiplier, flip the rounding, and add a max-volume cap. Its "Position size & risk" mode covers the other side: turning an account balance, a risk percentage and a stop-loss into a lot size.

Where Trepeat fits

In Trepeat the sizing rule is set per repeater: choose equity-ratio or a fixed multiplier, pick the rounding, and optionally cap the per-order volume, and every follower on that repeater is sized by that rule on each trade, using the same arithmetic shown above. If the two brokers define a lot differently, the lot is converted; if the accounts use different deposit currencies, equity ratio falls back to the multiplier. The calculator assumes the usual 0.01-lot step, while the engine snaps to whatever step your follower broker reports for that symbol, so on an instrument with a coarser step the placed size can differ from the preview by up to one step. Need different sizing for different accounts? Run a second repeater from the same source with its own rule. For the underlying source→follower model, see what a trade copier is. To see how any one copy was sized afterwards, hover its quantity on the Trades page.

Sizing also sets how deep a losing run can go. Measuring a result against the amount risked is in R-multiple explained, and how much it takes to climb back from a drawdown is in drawdown recovery math.