Position Size Calculator - risk-based lot sizing script - script for MetaTrader 5

Run the script on the chart of the symbol you plan to trade, enter how much you are willing to risk - a percent of equity or a fixed amount in your account currency - and your stop-loss distance, either in points or as a concrete price level, and it returns the lot size.

The calculation uses the symbol's real contract specification: tick size and tick value for the money-per-point math, and volume min/max/step for normalization. The result is rounded DOWN to the volume step, so the actual risk never exceeds your budget; the script reports the exact risk at the normalized size. It also estimates the required margin for the planned direction via OrderCalcMargin and warns clearly when the position would exceed your free margin, when the calculated size falls below the symbol minimum (i.e. even the minimum lot risks more than your budget), or when it must be capped at the symbol maximum.

The full report is printed to the chart Comment, the Experts journal, and a one-line Alert. Works on forex pairs, metals, indices and any symbol with valid contract specifications. It calculates only - it never places orders.