Lot Size Calculator
Wrong lot size is the fastest way to fail a prop firm challenge. Too big and one losing trade ends your day. Pick your firm below to get the exact lot size your account allows.
Lot Size Math for Prop Firm Traders
Lot size determines your dollar exposure per pip. Standard lots put $10 at risk per pip on major USD pairs. Mini lots put $1 at risk. Micro lots put $0.10 at risk. Understanding these numbers is the foundation of every trade on a prop firm account.
The calculation that matters is working backwards from your daily loss limit. If FTMO gives you a $5,000 daily loss limit and you want to risk no more than 1% of that limit per trade ($50), you need to size your position so that your stop loss distance in pips times pip value equals $50 or less. A 25-pip stop on EUR/USD at $10/pip per standard lot means your maximum position is 0.2 lots (2 mini lots).
Many prop firm traders make the mistake of sizing based on account balance rather than daily loss limit. On FTMO, 1% of a $100K account is $1,000 -- but the daily loss limit is only $5,000. Risking $1,000 per trade means five losing trades end your day. Sizing to 0.5-1% of the daily loss limit is the correct approach.
Frequently Asked Questions
What is a standard lot in forex?
A standard lot is 100,000 units of the base currency. On EUR/USD, one standard lot means you are buying or selling 100,000 euros. At a pip value of $10 per pip, a 50-pip adverse move costs $500. On a prop firm with a $1,000 daily loss limit, two losing trades at 50 pips each would breach your limit.
What lot size should I use on a prop firm challenge?
The right lot size depends on your account size, daily loss limit, stop loss distance, and risk percentage. Most experienced prop firm traders risk 0.5-1% of their daily loss limit per trade. On FTMO with a $5,000 daily loss limit, that means $25-50 per trade. With a 20-pip stop on EUR/USD, that corresponds to 0.125-0.25 lots per trade.
What is the difference between standard, mini, and micro lots?
A standard lot is 100,000 units (pip value $10 on most pairs). A mini lot is 10,000 units (pip value $1). A micro lot is 1,000 units (pip value $0.10). Micro lots are useful for fine-tuning position size, especially when your calculated lot size falls between round numbers.
How do I calculate lot size for a prop firm trade?
Use this formula: Lot Size = Risk Amount / (Stop Loss in Pips x Pip Value Per Lot). If you risk $50 with a 25-pip stop on EUR/USD (pip value $10/lot): Lot Size = 50 / (25 x 10) = 0.2 lots. This is 2 mini lots or 20 micro lots.