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Position Size and Stop Distance: The Arithmetic and Its Limits

Translate a self-chosen risk budget and price distance into a unit count while recognising execution risk.

One common way to explore position-size arithmetic is to decide on a money-at-risk budget and divide it by the difference between entry price and stop price. The result is a maximum mathematical unit count before other costs.

Worked idea

If an account amount is 10,000, a chosen risk budget is 1%, and the price distance to the stop is 5 per unit, the budget is 100 and the mathematical maximum is 20 units. This says nothing about whether the trade itself is sensible.

Stops do not guarantee a price

A stop can be affected by gaps, slippage, spread, fees, leverage, liquidity, and platform behaviour. In a fast market, the exit may occur at a worse price than the one used in the calculation.

Keep the boundary clear

Use the position-risk tool to understand the formula. It is not a risk-management system, investment advice, or a recommendation to trade.

Use the related calculator, then read our methodology, sources, and editorial policy. Spot an error? Contact the site.