Calculator
Position size calculator
How many contracts your stop and your risk actually allow, and what taking one more would really cost.
- Risk budget
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- This stop costs, per contract
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- Exact size the maths gives
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- Risk at this size
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- Stop in points
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Round down, always
The arithmetic rarely lands on a whole number. Wanting 2.4 contracts and taking 3 is not a small liberty: it is a 25% risk overrun on every trade, taken quietly, and it compounds across a session. The calculator prices that explicitly rather than leaving it as a rounding detail, because it is the single most common way a plan on paper becomes a different plan in practice.
When the answer is zero
Sometimes one contract already risks more than the budget allows. That is not a calculator failure, it is the honest answer, and it has exactly three fixes: a smaller contract, a tighter stop, or a larger account. Trading it anyway is a fourth option that is really just a decision to run a different risk than the one you chose.
What percentage is right
This page will not tell you. What it will do is show you the consequences: pair it with the risk of ruin calculator and watch what happens to the probability of a blown account as risk per trade climbs, holding your edge constant. The number that matters is not the one that feels brave, it is the one that survives a losing streak you will certainly have.
Your own numbers beat any calculator. Drop a NinjaTrader export on the Trade Lab and it works these figures out from the trades you actually took. It reads the file in your browser and nothing uploads.