Position Sizing for Prop Evals

Position sizing is choosing the number of contracts so the possible loss fits the account’s risk budget.

For prop evals, the risk budget is usually the drawdown room, not the advertised account size.

That one sentence can save a lot of resets.

Quick definition

Position sizing is the process of choosing trade size based on risk. In futures, that means translating stop distance into dollars per contract, then choosing the number of contracts that keeps the loss inside your planned risk.

The formula

Basic formula:

position size = risk budget ÷ risk per contract

Risk per contract depends on:

• ▸entry;
• ▸stop location;
• ▸point/tick value;
• ▸commissions;
• ▸slippage;
• ▸product volatility.

The prop firm twist

If a trader sees “$50K account” and risks like it is a personal $50K account, they are already off.

The real question is distance-to-bust. If the allowed drawdown is $2,000, a $400 risk trade uses 20% of the entire survival budget.

That may be acceptable for a specific system, but most traders are not thinking that clearly in the moment.

Why the 1% rule can fail

A lot of traders bring the 1% rule into prop evals.

On a $50K account, 1% is $500. If the actual drawdown room is $2,000, that $500 risk is 25% of the real failure budget. Four full losses can destroy the account before commissions, slippage, or tilt.

That is not conservative. That is oversized.

Minis vs micros

Micros are not just for beginners. Micros are for precision.

If the setup needs a wider stop, micros let the trader keep the idea without turning the trade into a drawdown event. A trader can always scale later. It is harder to recover after one full-size mistake breaches the account.

Common mistakes

• ▸sizing from headline account size;
• ▸treating max contracts as a suggestion;
• ▸using the same size in ES and NQ;
• ▸increasing size near the profit target;
• ▸refusing to use micros;
• ▸ignoring commissions and slippage;
• ▸not reducing risk after losses.

Prop eval sizing framework

Use this before every session:

1. ▸Current account balance/equity:
2. ▸Current failure line:
3. ▸Distance-to-bust:
4. ▸Max risk per trade as % of drawdown room:
5. ▸Product:
6. ▸Stop distance:
7. ▸Dollar risk per contract:
8. ▸Allowed contracts:
9. ▸Chosen contracts:
10. ▸Personal daily stop:

If you cannot fill that out, you are not sizing. You are guessing.

Bottom line

Position sizing is not about confidence. It is about staying alive long enough for the edge to matter.

The account does not care how good the setup looks. It only cares whether the loss fits inside the rules.