From risk in % to a number of MNQ contracts: the calculation step by step

Many traders pick their number of contracts in advance, then put their stop wherever the loss “stays bearable”. That is the reverse of the order that protects an account: the stop says where the scenario becomes wrong, and the size adapts to that distance.

In my prop firm challenge, the rule was written before the first session: 2% of the starting balance per trade during the evaluation, 1% on the funded account. The percentage does not move from one trade to the next. The number of contracts changes almost every time, because the stop is never at the same distance.

The risk in dollars: the capital multiplied by the chosen percentage. 1% of $50,000 is $500. The stop distance, in points: the gap between entry and stop. A long at 25,020 with a stop at 25,000 is 20 points.

The point value: the CME sets it in the contract specification, and it is the same at every broker. MNQ is worth $2 a point, and its smallest price step, the 0.25-point tick, is worth $0.50. NQ is worth $20 a point: one NQ carries the exposure of ten MNQ. On the diagram, the distance that matters runs from entry to stop, not from entry to target.

The risk of one contract is the stop distance multiplied by the point value: 20 points × $2 = $40. The number of contracts is the dollar risk divided by that unit risk: 500 / 40 = 12.5.

Then you round down, always: 12 contracts, or $480 of actual risk. Rounding to 13 would make $520, more than you decided to risk. The table applies the same $500 rule to four stops: the wider the stop, the fewer contracts you take, and the possible loss stays the same.

The whole calculation hangs on one decision: where the stop goes. That is where I use FTS Liquidity Sweep Pro. The signal marks the candle that has just swept the liquidity; if I am buying, my stop goes just below its wick, where the scenario becomes wrong. The indicator draws neither the stop nor the size: it gives me the marker, I measure the distance and I do the calculation.

On October 7, 2026, the last session of my evaluation, I bought 18 MNQ after one of the indicator’s buy signals. Those 18 contracts did not come from habit: they came from the 2% rule and the distance to my stop that day. After a signal with a longer wick, the same rule would have given fewer contracts.

Fees and slippage first: commission is charged per contract, and a stop that gets hit can be filled one tick further. With 12 MNQ, one tick of slippage costs $6 more. Nothing dramatic, but enough to keep a margin rather than aim for the last dollar.

Next, at a prop firm, the balance shown is not the money you can lose: what counts is the distance to the maximum loss threshold. Those rules differ from one firm to another and change often: read the ones for your account on the firm’s own site. Finally, granularity: with $500 of risk and a 30-point stop, one NQ risks $600, so zero contracts. That is exactly what MNQ is for.

The calculation is simple, but it happens at the worst moment: the signal has just appeared, price is moving, and a misplaced decimal comes fast. I no longer do it in my head. The site’s position size calculator takes the capital, the percentage and the stop, and rounds down for you.

The number you get is not a recommendation: it is what your own rule allows. If it looks too small, it is the percentage you should question, not the rounding. And log the size you took on every trade in your journal: a gap between the calculated size and the size you actually traded is a mistake in its own right.