Position Size Calculator

A position size calculator works out the exact quantity of an instrument (lots, shares, contracts, or coins) that you should trade so that if your stop-loss is hit, you lose only your pre-defined risk amount (typically 1–2% of account equity). It’s the single most important piece of risk arithmetic in trading.

Forex position size = (Account balance × Risk %) ÷ (Stop loss in pips × Pip value per lot). For a $10,000 USD account risking 1% with a 20-pip stop on EUR/USD: $100 ÷ (20 × $10) = 0.5 standard lots. The calculator above does this and adjusts for JPY pairs and cross-currency conversions automatically.

Position size math is the same idea across all three markets. Risk amount ÷ (stop distance × per-unit value), but the unit you size in changes. Forex outputs lots (1 standard lot = 100,000 units of the base currency) and uses pip-based stops. Crypto outputs coin units (or contracts on a perp exchange), with the stop entered in price terms. Stocks outputs whole shares, rounded down so you never exceed your risk dollar amount. The calculator above flips into the right unit when you switch tabs at the top. JPY pairs use a 0.01 pip (not 0.0001), and crypto perp leverage multiplies notional exposure. The tool factors both automatically so you never have to convert manually.

JPY pairs use 0.01 as one pip instead of 0.0001. The calculator detects this from the pair name and adjusts automatically. For cross pairs (EUR/JPY, GBP/CHF) where neither the base nor the quote currency matches your account currency, the calculator pulls a cross-rate and converts the pip value into your account currency. Prices and currency conversions use real market quotes, delayed up to a minute.

The 1% rule says you should never risk more than 1% of your trading account on a single trade. With proper position sizing, even a 20-trade losing streak (which any trader will eventually have) only draws the account down ~18%. Risk 3% instead and that same streak takes the account down 46%. Risk 5% and you’re at -64%. The 1% rule is the difference between a career and a blow-up.

For a $100K prop-firm Phase 1 a 0.5–1% per-trade risk is the desk consensus. It gives you 4–5 consecutive losses of headroom before the 5% daily loss cap fires, and roughly 8–10 losses before the 10% trailing-drawdown rule does. Some traders run 0.5% during the first week to absorb a bad streak, then scale to 1% once safe. Anything above 1.5% per trade and one bad day can end the challenge. The position size calculator above takes your risk %, stop distance, and pair, and outputs the lot count that exactly matches that risk. No mental math, no rounding errors. For a full audit of how the size interacts with daily caps, trailing drawdown, consistency rules, and weekend-hold restrictions across the major prop firms, run it through the funded-account compliance audit.

Position size and margin are two different questions that traders constantly conflate. Position size is the risk answer. If my stop-loss is hit, exactly how much money do I lose? A 0.5-lot EUR/USD position with a 100-pip stop risks $500. That’s the number this calculator produces. Margin is the leverage answer. Can my broker even afford to let me open this trade? That same 0.5 lot is roughly $54,000 of notional exposure; at 1:30 leverage your broker holds $1,800 of free margin from your account to back it. Both numbers matter, and they’re independent: you can have plenty of margin and still blow up from oversizing, and you can be perfectly sized and still hit a margin call by stacking too many positions. For the margin side specifically use our Margin Calculator.

Yes, the calculator on this page is free with no signup. A free CleaRank account adds the trading simulator, a trade journal and a portfolio, with no card needed. Pro and Unlimited add CleaRank Financial AI, saved scenarios, PDF and CSV exports and the Prop Firm Auditor. Both are billed yearly: Pro is $103.20 for your first year ($8.60 a month), then $172.00 a year.