Position Sizing

Position sizing is the decision of how many contracts (or shares, or lots) to trade on a given entry. As a general trading discipline, it's usually driven by account size, risk tolerance, and how far away a stop-loss sits — a trader risking 1% of a $50,000 account on a 10-tick stop will size very differently than one risking the same percentage on a 40-tick stop.

In a trade copier, position sizing takes on a second meaning: converting the leader's trade size into an appropriate size for each follower account. Because follower accounts are often different sizes — a $25,000 evaluation account and a $100,000 funded account, for instance — a straight 1:1 copy of contract count rarely makes sense.

Getting follower sizing wrong is one of the more common ways prop firm traders damage an account through copying itself, independent of whether the underlying trade wins or loses. A follower sized too large relative to its account can blow through a daily loss limit on a single trade the leader treated as routine.

This is why copiers use a multiplier rather than a fixed contract count: it lets the same leader trade scale up or down correctly across accounts of very different sizes, funded through different firms, without the trader manually recalculating size for every account on every trade.

MimikTrader uses multiplier-only sizing. Each follower account has its own multiplier, and its order quantity is calculated as followerQty = max(1, ceil(leaderQty × multiplier)) — the leader's quantity times the follower's multiplier, rounded up, with a floor of one contract. Every follower's size always scales from the leader's trade through that multiplier; there is no mode that trades a set contract count regardless of the leader's size.