Position Sizing When Copying Trades: Equity-Ratio vs Fixed Lot
Copying a trade isn't copy-paste — the lot is scaled to each account. Equity-ratio vs fixed multiplier, rounding, broker minimums and volume caps, with worked examples.
27 Jun 2026 · 5 min read
Copying a trade isn't quite copy-paste. If your source account opens 1.0 lot, repeating exactly 1.0 lot onto a follower with a tenth of the balance would over-expose it badly. So a copier scales the size to each follower account. This is arithmetic, not advice — it tells you the proportional lot for the inputs you give, nothing about what you should risk.
Fixed lot / fixed multiplier
The simplest rule is a fixed multiplier: every follower trades the source lot times a constant. At 0.5× a 1.0-lot source becomes 0.50 on every follower; at 2× it becomes 2.00 — regardless of each follower's balance. It's 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.
Equity-ratio sizing
Equity-ratio scaling sizes each follower by its own balance relative to the source:
follower lot = source lot × (follower balance ÷ source balance)
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.
| Source 1.0 lot @ $50k | Follower balance | Equity-ratio lot | Fixed 0.5× |
|---|---|---|---|
| Follower A | $100,000 | 2.00 | 0.50 |
| Follower B | $50,000 | 1.00 | 0.50 |
| Follower C | $25,000 | 0.50 | 0.50 |
Rounding, minimum lot, and a volume cap
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 always gets at least the intended size.
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.
Try the numbers
The lot size calculator runs exactly this maths — switch it to "Copy sizing" to 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 — once — and every follower is sized automatically on each trade, using the same arithmetic shown above. The calculator and the live engine share the formula, so what you preview is what gets placed. For the underlying source→follower model, see what a trade copier is.