Position size calculator
Your capital, the risk you accept and the stop distance: how many contracts or lots, rounded down so you never go past what you decided to risk. No sign-up.
Position size
2 MNQ contracts
- Target risk
- $100 (1%)
- Actual risk at this size
- $80 (0.8%)
Rounded down, never to the nearest: rounding up would have you risk more than planned. Hence the gap between the two lines.
The calculation ignores commissions, slippage, gaps that can take you out beyond the stop, and the margin your broker requires. It answers one question: how much, so you risk no more than planned if the stop is hit.
The size follows from the stop, not the other way round
The order of the decisions matters more than the arithmetic. First the stop, placed where the trade idea is invalidated: below the low that was swept, beyond the level that was supposed to hold. Only then the size, chosen so that this stop costs the share of capital you set in advance.
Doing it the other way round — starting from a size you want to take and pulling the stop in so the risk "fits" — is the most common mistake, and the most expensive. The stop is then no longer somewhere that means anything; it is somewhere that suits the account, and the market has no reason to respect it.
Read next: Swing High / Swing Low · ICT strategies
Why the result is always rounded down
You cannot buy 2.5 contracts. Rounding to 3 would risk 120 instead of 100; rounding to 2 risks 80. The calculator always takes the second option and shows both figures, the target risk and the actual risk, so the gap is visible rather than hidden.
Risking a little less than planned costs almost nothing over a series of trades. Risking a little more, trade after trade, is exactly the drift that turns a 1% rule into a 1.5% rule without anyone ever deciding it.
When even the smallest position is too big
With $2,000 and a 30-point stop on the Nasdaq, a single NQ contract risks $600, or 30% of the account. Even MNQ, ten times smaller, risks $60, or 3%. The arithmetic does not lie: this account cannot take this trade within the rules. That is why the smallest tradable size should be the first criterion when choosing an instrument or a broker, and it almost never appears in comparisons.
Three honest ways out remain: a smaller instrument (micros on futures, 0.01 lot on forex), a setup whose invalidation sits naturally closer, or more capital — which is what an account funded by a prop firm provides. The fourth, pulling the stop in so the size fits, is not one.
Read next: Prop firms