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Guide · Position sizing

How to Calculate Position Size

The short answer

Fix the loss first, then divide by the stop distance. Everything else is arithmetic.

Why it works this way

The reasoning is set out in full on the live site. In this build the article carries its position, the calculator that does the arithmetic, and the assumptions the answer depends on, so the structure and the internal linking can be reviewed before the prose is written.

What will not change is the shape: a claim in the first line, the method that supports it, the number it produces, and a link to the tool so a reader can put their own inputs in rather than take ours.

What this depends on

MethodThe rule is stated precisely enough to run, and the same rule produces every figure quoted.
MeasuredWhere a number comes from our own testing it carries its sample size and its data vintage.
LimitsCosts, slippage and non-USD accounts change the arithmetic. See methodology.