Position size calculator: how to size forex, crypto and stock trades

The Universal Position Sizing Formula

Every disciplined risk-management system starts with the same foundational rule: decide the maximum dollar amount you are willing to lose if your stop-loss is hit, and work backwards from your stop distance to the number of units you can buy or short. Whether you trade US equities on NYSE, currency pairs in spot forex, or linear perpetual contracts in crypto, the core identity is identical:

Position Size (Units) = Dollar Risk Budget ÷Price Stop Distance per Unit, where Dollar Risk Budget = Account Capital × (Risk % ÷ 100) and Price Stop Distance = |Entry Price − Stop-Loss Price|.

Why do retail traders still blow up accounts if the formula is so simple? Because each market quotes contract multipliers, minimum lot steps and round-trip transaction fees differently. Below we walk through the exact mechanics for stocks, forex and crypto, and show how you can verify every number interactively in the TradeProfy Trade Planner or our standalone Position Size Calculator.

1. Sizing US & Global Stock Trades (Shares & Fractional Shares)

In cash equities and ETFs, one unit equals one share. After computing the raw share count rawUnits = riskAmt ÷ |entry − stop|, you must round down to the nearest whole share (floor(rawUnits)) unless your broker supports fractional share routing—so your actual risk never exceeds your intended dollar cap.

Worked Example: US Stock Breakout

You hold a $10,000 account and risk 1.0% ($100.00) on a long setup entering at $100.00 with a technical stop-loss below support at $95.00 and a profit target at $112.00, paying $1.00 commission per order:

• Stop distance per share: |$100.00 − $95.00| = $5.00.
• Share count: floor($100.00 ÷ $5.00) = 20 shares ($2,000 total position value, requiring no margin leverage).
• Net-of-fee check: With $2.00 in round-trip commission (0.02R), your stop-out loss is −$102.00 (−1.02R) and your target net profit is +$238.00 (+2.38R), producing a true net reward-to-risk ratio of 2.333 : 1.

2. Sizing Spot Forex Trades (Pips, Standard, Mini & Micro Lots)

In foreign exchange, positions are sized in lots rather than individual currency units: 1 Standard Lot equals 100,000 units of the base currency, 1 Mini Lot (0.10) equals 10,000 units, and 1 Micro Lot (0.01) equals 1,000 units. For pairs where USD is the quote currency (EUR/USD, GBP/USD, AUD/USD), a 1-pip (0.0001) move on 1.00 standard lot equals exactly $10.00 ($1.00 per mini lot, $0.10 per micro lot).

Worked Example: EUR/USD Intraday Setup

With a $10,000 USD account risking 1.0% ($100.00), you buy EUR/USD at 1.0800 with a stop-loss at 1.0770:

• Stop distance in pips: (1.0800 − 1.0770) ÷ 0.0001 = 30 pips.
• Raw lot size: $100.00 ÷ (30 pips × $10.00/pip/lot) = 0.3333 lots.
• Rounded down to 0.01 micro-lot step: 0.33 lots (3 mini lots + 3 micro lots), resulting in an actual cash risk of $99.00 before spread and commission.

3. Sizing Crypto Spot & Linear Perpetual Futures

In linear USDT/USD perpetual futures (BTCUSDT, ETHUSDT), leverage changes the margin required to open the position and determines your liquidation price, but it does not change the position size dictated by your stop-loss! Using the same example ($10,000 capital, 1% risk = $100, entry $60,000, stop $58,800, 10× leverage), your position size is $100 ÷ $1,200 = 0.083333 BTC ($5,000 notional). At 10× leverage, only $500 of margin is blocked, and estimated isolated liquidation sits at $54,300—safely below your $58,800 stop-loss.

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