Position Size Calculator with Fees and Quantity Steps

Choose the budget before the quantity

The money budget is account equity × your entered risk percentage / 100. Use equity and cost values in the same currency. The default 1% is a hypothetical example, not a recommendation for your account.

Entry and stop define a price distance. A stop below entry describes long-position loss distance; a stop above entry describes short-position loss distance. The calculation uses the absolute distance and rejects a zero distance.

Convert price movement into money

One unit’s modeled price loss is absolute(entry − stop) × point value. Add round-trip costs per unit to obtain the total variable risk per unit.

For a share quoted in the account currency, a point value of 1 means a one-unit price move changes one share’s value by one currency unit. Derivatives may have another multiplier. Confirm your instrument’s contract specifications before entering a point value.

Reserve costs before rounding

Raw quantity = max(0, (risk budget − fixed round-trip costs) / variable risk per unit). The tool then rounds down to a whole number of the entered quantity increments.

Variable costs belong in the per-unit field. Fixed costs belong in the fixed field. Do not put the same commission in both. If no minimum-sized order fits, quantity is zero and the model assumes no order and no fees.

Follow the default example

Equity of 10,000 and a 1% risk budget give a budget of 100. Entry 100 and stop 97.5 create 2.50 of price risk per unit. Adding 0.02 of per-unit costs gives 2.52. Reserve fixed costs of 2 first.

Raw quantity is 98 / 2.52 = 38.8889. At a one-unit increment, the result is 38 units. Modeled loss is 38 × 2.52 + 2 = 97.76, leaving 2.24 unused. Rounding up to 39 would exceed the budget.

Separate risk budget from buying power

A position can fit this loss budget and still require more cash or margin than is available. Notional exposure, borrowing rules, liquidation thresholds, and portfolio concentration are separate checks.

The calculator does not estimate margin from the stop distance. A tight planned stop is not a substitute for adequate capital or an understanding of how the instrument is financed.

Know the execution boundary

The result is conditional on an exit at the entered stop price and on the cost estimates. A gap or worse fill can make the actual loss larger. Minimum commissions and tiered fees may also differ from the linear cost model.

If several positions can lose together, their combined exposure matters. Sizing one position in isolation does not assess portfolio-level risk.

What this tool does not calculate

• Linear P&L and entered cost estimates only; not a margin or suitability assessment.
• Stop orders do not establish a guaranteed maximum loss.
• Actual venue quantity increments and fee schedules must be checked separately.