Position-sizing methods for algorithmic systems

The desired cash risk must be translated through stop distance, tick size, tick value, volume step, and contract specifications. The same lot value cannot be assumed across brokers or symbol suffixes.

Round the result to a valid volume step and re-check the actual cash risk after rounding. Small accounts can be materially affected by a minimum lot that is larger than the calculated ideal size.

Fixed-lot sizing is simple but changes in risk as volatility and stop distance change. Fixed-cash or percentage-of-equity sizing keeps risk more consistent when the contract calculation is correct. Volatility sizing adjusts exposure to a measured range, but it can increase size after quiet periods just before volatility expands.

A sizing formula should have maximum volume, maximum cash risk, margin checks, and a safe response when symbol data is missing. If the calculated volume is invalid or unusually large, refusing the trade is safer than guessing.

Log the requested risk, calculated volume, rounded volume, stop distance, and broker values so a sizing issue can be diagnosed after the fact.