Check the inputs behind a position-size calculation
Why stops, quantity steps, costs and capital caps matter.
VertexFiles editorial · Updated 6 September 2026
Use one consistent price unit
Account balance, entry, stop, target and costs must use the same currency and compatible per-unit pricing. This tool does not convert currency, contract multipliers or tick values. For contracts with different quote conventions, convert the values independently or use a calculator designed for that instrument.
Check the direction of the trade
For a long scenario, the stop is below entry and the target above entry. For a short scenario, those relationships reverse. A zero price difference does not define a usable risk distance. The tool rejects invalid relationships instead of returning an infinite or misleading quantity.
Round quantity down, not up
The risk budget is divided by the entry-to-stop distance plus the entered round-trip per-unit cost. Quantity is then capped by the entered notional limit and rounded down to a quantity step. A result of zero means the inputs cannot accommodate one step; it is not an instruction to raise your risk.
Understand what the stop estimate omits
A stop price is not a guaranteed fill price. Gaps, liquidity, slippage and additional charges can produce larger losses. The calculation does not model liquidation, margin requirements or live market conditions. It is a planning illustration, not a recommendation to place a trade.