Inconsistent sizing — Large, unexplained variation in position size between trades, which firms flag as gambling behaviour rather than a managed strategy.
How inconsistent sizing works in prop trading
Firms compare your typical position size against your largest. Where one trade at five times normal size produced most of the account's profit, the review concludes the result was a bet rather than an edge. Some firms publish a hard ratio — no trade above two or three times the average — while others apply it as a discretionary payout check.
It is closely related to the consistency rule but measures a different thing: consistency looks at profit distribution across days, inconsistent sizing looks at risk distribution across trades. An account can satisfy one and fail the other. Both are usually evaluated at the payout request, which is the worst time to discover either.
Key points
- Measured as largest position size against typical size, commonly capped at two to three times.
- Distinct from the consistency rule, which measures profit by day rather than size by trade.
- Usually applied at the payout review rather than blocked live.
- Deliberate scaling that follows a documented plan is normally defensible; ad-hoc size spikes are not.
Also known as
- size inconsistency
- lot inconsistency
- erratic sizing
- sizing rule
Frequently asked questions
What is the sizing rule at prop firms?
Where one exists, it caps how far a single trade's size may deviate from your average — commonly two to three times. The intent is to stop a single oversized bet from carrying the account, and it is normally checked when a payout is requested.
Can I increase my position size on a funded account?
Yes, within the contract cap and any sizing rule. Increasing gradually and consistently is fine; jumping to several times your normal size for one trade is what triggers review, particularly when that trade is a large share of total profit.
Put this into practice
Inconsistent sizing is described here as a plain-language educational definition. Firms, platforms, and account programs may apply different conditions or calculations. Verify the current official terms before using this definition to make an account decision.