Every copier asks you the same question during setup, usually in a dropdown, usually without explaining the consequences: how should the follower's position size relate to the master's?
Answer it carelessly and you will discover the consequences during a drawdown, which is the worst time to learn anything. Here are the three real options, what each one actually does, and how each one fails.
Fixed lots
The follower trades a constant size — 0.10 lots per copied trade — regardless of what the master did or what either account is worth.
Use it when you are testing a new master and want a hard, predictable ceiling on what any single trade can do to you.
How it fails: it discards the master's own risk management. If the master sizes up on high-conviction setups and down on marginal ones, fixed lots flattens that into noise — you take the same risk on their best idea and their worst. You have not reduced risk so much as removed information.
Multiplier (proportional)
The follower trades the master's size multiplied by a constant. Master takes 1.0 lots, multiplier is 0.25, follower takes 0.25 lots.
Use it when the two accounts are similar in size, or when you deliberately want the master's conviction preserved.
How it fails: it silently assumes the accounts stay in proportion. They do not. The master doubles after a good quarter and keeps sizing to its balance; your follower did not double, but its multiplier did not change either. What was a comfortable 1% risk per trade drifts to 2%, then 3%, with nothing alerting you. A multiplier set once is a risk setting that decays.
Risk percent (balance-proportional)
The follower sizes each trade so the distance to the stop loss represents a fixed percentage of its own equity. Master risks 1% of its account; follower risks 1% of its account, in its own lots.
Use it when accounts differ meaningfully in size — which is most of the time.
How it fails: it requires a stop loss on the trade to compute anything. A master that enters first and sets stops afterwards, or manages exits manually, gives the copier nothing to size against. Different copiers handle that gap differently — some skip the trade, some fall back to a default, some use a configured worst-case distance. Find out which yours does before it happens, because a silent fallback to a default size is how the sizing mode you chose stops being the sizing mode you are running.
A sizing rule you have not tested against a stop-less trade is a sizing rule you have not chosen.
The comparison, plainly
- Predictable worst case per trade: fixed lots.
- Preserves the master's conviction: multiplier.
- Scales correctly across unequal accounts: risk percent.
- Needs the least from the master's discipline: fixed lots.
- Most likely to drift silently over months: multiplier.
For most people copying their own strategy into accounts of different sizes, risk percent is the right default, with a hard maximum lot size layered on top as a backstop. The maximum is what saves you from a mis-keyed stop distance turning one trade into an account-ending one.
Two settings people forget
Rounding. A 0.13-lot calculation on a broker with a 0.01 minimum is fine. The same calculation on an account with a 0.1 minimum rounds to 0.1 — a 23% overshoot on every trade, permanently, invisibly. On small accounts, rounding is your sizing mode.
Partial closes. If the master scales out of half a position, does the follower close half of its own, or a proportional amount of the original? Copiers differ, and the difference compounds across a multi-leg exit. Test it on a demo follower with a deliberately messy trade before you trust it with money.
None of this is complicated, but all of it is load-bearing. Pick the mode for the relationship between the accounts, set a maximum lot backstop, then verify both with a demo follower and a handful of real trades — including one you close in pieces.
