Max Position Size Rules Explained for Prop Firm Traders
Max position size rules tell you exactly how many contracts you’re allowed to hold at once. If you ignore them, you’ll violate your prop firm’s risk policy even if the trade wins. Understanding max position size rules is non-negotiable if you want to keep an evaluation or funded account alive.
What Are Max Position Size Rules?
Max position size rules define the largest number of contracts you can have open at any one time on that account. It doesn’t matter how “good” the setup looks. If the rule says three contracts and you punch in four, you’re in violation.
These rules sit alongside things like soft and hard breach rules and scaling plans. Together, they decide if you stay in the game or get kicked out.
How Max Position Size Is Usually Set
Most futures prop firms set max position size based on:
- Your account size (50k, 100k, etc.)
- Whether you’re using regular contracts or micros
- Whether there’s a scaling plan in place
The firm gives you a clear number in their rules. Example: “Maximum 10 micro contracts” or “Maximum 3 standard contracts.” Go past that, and you’re done, regardless of P/L.
Max Position Size vs Scaling Plan
Max position size rules and scaling plans are related but not the same thing:
| Rule Type | What It Controls | When It Changes |
|---|---|---|
| Max Position Size | Absolute ceiling on contracts | Rarely changes during the evaluation |
| Scaling Plan | Contracts allowed based on balance | Changes as account grows |
Some firms give a flat max position size. Others tie it directly to a scaling plan like you saw in Scaling Plans Explained.
What Counts Toward Max Position Size
Prop firms look at overall exposure, not just one market. That means they may count:
- All contracts across all instruments (ES, NQ, CL, etc.)
- Both micros and minis in the same symbol family
- Hedged positions if the firm’s rules are strict
If your rules say “10 micros max,” then 6 MES + 4 MNQ could already be over the combined risk they intended, depending on how they define it. Some firms are vague here, so you assume the stricter interpretation if you’re smart.
How Max Position Size Violations Are Triggered
Violations are simple: if your open position size exceeds the allowed max, you’re in trouble. Common ways traders screw this up:
- Stacking scale-in orders without checking total size
- Running multiple instruments at once and losing track
- Brute-forcing revenge trades after a loss
Depending on the firm, this can be either a soft breach (they cut you off for the day) or a hard breach that kills the account. If you don’t know the difference yet, go read the soft vs hard breach article and then come back.
How to Stay Inside Max Position Size Rules
Staying compliant with max position size rules is just discipline:
- Write your max contracts on a sticky note next to your screen
- Pre-define your size per setup and don’t exceed it
- Use fixed bracket templates in your platform so you don’t fat-finger size
- Count combined size if you trade multiple products at once
The goal is boring: never be in a position where you “hope” support holds while also knowing you’re oversized according to the rules.
Max Position Size and Risk Management
Max position size rules are not your risk plan; they’re the ceiling. You usually shouldn’t be trading at the ceiling. If your daily loss limit is small relative to your normal stop size, hitting the max position size is a great way to nuke the account in one or two trades.
Use max position size as the outer boundary, not your default. If three micros per trade keeps you safe, don’t go to ten just because the prop firm allows it.
Final Takeaway on Max Position Size Rules
Max position size rules are simple: they cap how big you can get. Break that cap and you violate the account, even on a winning trade. Know your number, trade below it most of the time, and treat the max position size rules as a hard line you never cross.