Calculateur de taille de position

What this calculates

Position size follows from two decisions you make first: how much of the account you are prepared to lose on this one idea, and the price at which the idea is wrong. Divide the first by the distance to the second and you have the largest position consistent with your own limit. That is the whole computation.

Why sizing matters more than entry

Losses are asymmetric: a 50% loss requires a 100% gain to recover, and a 90% loss requires a 900% one. Surviving is a precondition for everything else, and survival is a function of size rather than of timing. Most of the attention in this field goes to the entry, which is the part you control least.

What it cannot account for

Stops are not guarantees. In a fast market an order can fill well below its level, and a gap can skip it entirely. Leverage makes both worse. Fees, funding costs, spread and tax are all outside this arithmetic. And none of it addresses the more important question of whether to hold a position at all.