Position Size Calculator
Find the exact lot size that keeps a loss within your risk budget. Built for prop firm rules: 1% risk, 5% daily drawdown, and everything around them.
Input
$10.00/pip · 2026-09-30 · ECB reference
Auto-filled from the selected pair. Override if your broker quotes differently.
Advanced settings
Refine the calculation with your broker's real costs. Spread and commission trim the effective position size.
Added to the stop distance. A wider spread reduces the position size.
Round-trip commission per standard lot. Typical: $3–$7.
Used to calculate the margin required on the position.
Auto-filled from the live feed. Override for limit orders.
Pip size: 0.0001 · Base: EUR · Quote: USD
Result
Low margin usage: you have flexibility to add positions or scale in. Risking 1% or less per trade is ideal for prop firm challenges.
How this is calculated
lots = (balance × risk %) ÷ ((stop loss + spread) × pip value per lot + commission per lot)
The risk budget comes first: your account balance multiplied by the risk percentage. That figure is the most this trade is allowed to cost you, and everything else divides into it.
The stop distance used is your stop loss plus the spread, because the spread is crossed before the stop can trigger. A wider spread therefore produces a smaller position for the same budget rather than a larger loss.
Round-trip commission is added to the cost of a single lot instead of being charged on top, so it is paid out of the same budget. Set commission to zero and the equation collapses to the textbook version. One standard lot is 100,000 units of the base currency, or 100 troy ounces for gold.
Worked example: a $10,000 balance risking 1% gives a $100 budget. A 20-pip stop plus a 1-pip spread is an effective distance of 21 pips. At $10 per pip per standard lot with no commission, 100 ÷ (21 × 10) = 0.48 standard lots.