Educational guide

Position Sizing Math: A Neutral Explanation

Position-size math answers a narrow question: if you choose a monetary risk budget and a per-unit distance to a stop, how many whole units fit inside that budget?

The formula

Risk budget equals account value multiplied by a percentage you choose. Risk per unit equals the absolute difference between entry and stop. Dividing the budget by per-unit risk produces a raw unit count.

The percentage is an assumption, not an answer

Many educational resources promote a fixed percentage as a rule. PreBreakout does not. The calculator asks you to provide the percentage because selecting an appropriate risk budget depends on circumstances outside a simple formula.

Why rounding matters

If the raw result is 50.8 units and the instrument cannot be traded fractionally, 50 whole units fit inside the modeled budget while 51 may exceed it. The calculator rounds down to whole units and shows the theoretical exposure separately.

What the simple model omits

Gap risk, slippage and execution can make actual loss larger than the planned entry-stop distance. Leverage and broker margin rules can also constrain position size independently of the risk formula.

Keep the distinction clear: a chart label describes geometry or past observations. It is not, by itself, a forecast, probability estimate or instruction to buy or sell.

Try the math yourself

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