The Position Sizing Formula (Plain English)
Every position size calculation answers one question: how many lots/shares/contracts can I trade so that if my stop loss gets hit, I lose exactly X% of my account?
That's it. Three inputs, one output. Let's break each piece down:
| Input | What It Means | Example |
|---|---|---|
| Account Balance | Your current account equity (not initial deposit) | $10,000 |
| Risk % | Maximum you're willing to lose on this trade | 1% = $100 |
| Stop Loss Distance | Pips, points, or dollars between entry and stop | 25 pips |
| Value Per Unit | How much 1 pip/point costs at 1 standard lot/share/contract | $10/pip (EUR/USD) |
Output: $100 ÷ (25 × $10) = 0.4 standard lots.
The Mistake That Makes 1% Risk Actually 3%
Most traders pick a "comfortable" lot size and use it for every trade. Trading 1.0 lot with a 10-pip stop = 1% risk on a $10K account. But the same 1.0 lot with a 30-pip stop = 3% risk. Same lot size, 3× the risk. Without calculating position size per trade, your risk is random. The formula eliminates this.
Example 1: Forex (EUR/USD)
This is the most common position sizing scenario. Let's walk through it step by step.
The Setup
- Account: $10,000
- Risk: 1% = $100
- Trade: Short EUR/USD at 1.0850
- Stop loss: 1.0875 (25 pips above entry)
- Target: 1.0800 (50 pips below entry) → 2:1 R:R
Step-by-Step Calculation
- Dollar risk: $10,000 × 1% = $100
- Stop distance: 1.0875 − 1.0850 = 25 pips
- Pip value: EUR/USD, 1 standard lot = $10/pip
- Position size: $100 ÷ (25 pips × $10) = 0.40 lots
What If the Stop Is Wider?
| Stop Distance | Position Size (1% risk) | Position Value | Max Loss |
|---|---|---|---|
| 15 pips | 0.67 lots | $67,000 | $100 |
| 25 pips | 0.40 lots | $40,000 | $100 |
| 50 pips | 0.20 lots | $20,000 | $100 |
| 100 pips | 0.10 lots | $10,000 | $100 |
Notice: The max loss is always $100 regardless of stop distance. That's the point — position sizing keeps risk constant even when stop distance varies. Wider stop → smaller position. Tighter stop → larger position. The risk stays the same.
Pip Values for Common Pairs
| Pair | Pip Value (1 Std Lot) | Notes |
|---|---|---|
| EUR/USD | $10.00 | USD is quote currency → always $10 |
| GBP/USD | $10.00 | Same — USD quote |
| USD/JPY | ~$6.60 | Varies with USD/JPY rate |
| USD/CHF | ~$11.20 | Varies with USD/CHF rate |
| EUR/GBP | ~$12.50 | Varies with GBP/USD rate |
| GBP/JPY | ~$6.60 | Varies with USD/JPY rate |
For cross-pairs where neither currency is your account currency, pip values change with exchange rates. Use the lot size calculator to get the exact value for your pair and account currency.
Example 2: Crypto (BTC/USDT)
Crypto position sizing works the same way — the formula is identical, only the units change.
The Setup
- Account: $5,000 (on exchange or futures)
- Risk: 1% = $50
- Trade: Long BTC at $95,000
- Stop loss: $93,000 (2.1% below entry)
- Target: $99,000 (4.2% above entry) → 2:1 R:R
Step-by-Step Calculation
- Dollar risk: $5,000 × 1% = $50
- Stop distance in dollars: $95,000 − $93,000 = $2,000 per BTC
- Position size: $50 ÷ $2,000 = 0.025 BTC
- Position value: 0.025 × $95,000 = $2,375
Leverage Doesn't Change the Risk
This is the #1 misconception in crypto trading. Let's prove it:
| Leverage | Position Size | Margin Required | Loss if Stopped Out | Risk % |
|---|---|---|---|---|
| 1× (spot) | 0.025 BTC ($2,375) | $2,375 | $50 | 1% |
| 5× | 0.025 BTC ($2,375) | $475 | $50 | 1% |
| 10× | 0.025 BTC ($2,375) | $237.50 | $50 | 1% |
| 20× | 0.025 BTC ($2,375) | $118.75 | $50 | 1% |
Same position, same stop, same loss — regardless of leverage. Leverage only changes how much margin you need to hold the position. It does not change the dollar risk. Higher leverage becomes dangerous only when traders use it to take larger positions than the formula allows.
Example 3: Stocks (AAPL)
Stock position sizing is the simplest because there's no pip value or contract multiplier — 1 share = 1 share.
The Setup
- Account: $25,000
- Risk: 1% = $250
- Trade: Long AAPL at $195.00
- Stop loss: $190.00 ($5 below entry)
- Target: $207.50 ($12.50 above entry) → 2.5:1 R:R
Step-by-Step Calculation
- Dollar risk: $25,000 × 1% = $250
- Stop distance: $195.00 − $190.00 = $5.00 per share
- Shares: $250 ÷ $5 = 50 shares
- Position value: 50 × $195 = $9,750
The Position Value Trap
Many stock traders think "I'm risking $9,750 on this trade." You're not. You're risking $250. The $9,750 is your position value, not your risk. Your risk is always: shares × stop distance. If AAPL gaps through your stop, your actual loss could exceed $250 — but that's gap risk, not a position sizing error.
Calculate Your Position Size
Use the formula from this guide instantly — enter your account size, risk percentage, and stop loss distance:
Handles forex, crypto, stocks, and futures. Adjusts for account currency automatically.
5 Position Sizing Mistakes (With Real Math)
1. Using Fixed Lot Size
| Trade | Lot Size | Stop | Actual Risk | Intended Risk |
|---|---|---|---|---|
| EUR/USD #1 | 1.0 lot | 10 pips | $100 (1%) | 1% ✅ |
| EUR/USD #2 | 1.0 lot | 30 pips | $300 (3%) | 1% ❌ — actual 3× |
| EUR/USD #3 | 1.0 lot | 50 pips | $500 (5%) | 1% ❌ — actual 5× |
Impact: Trade #3 has 5× the risk of Trade #1, despite using the same lot size. One wide-stop loss wipes out 5 narrow-stop wins.
2. Not Adjusting for Account Changes
You start with $10,000 and calculate 1% = $100. After a drawdown to $8,000, 1% is now $80 — but you're still trading as if it's $100. This means you're actually risking 1.25% on a smaller account, accelerating the drawdown. Always calculate from current equity, not starting balance.
3. Forgetting Spread in the Calculation
Your stop is 20 pips away. But the spread is 2 pips. Your effective stop is 22 pips. At 1 lot, that's $220, not $200 — a 10% increase in risk. On tight stops (10-15 pips), spread can add 15-20% to your intended risk. Account for spread in your calculation: use (Stop + Spread) as your stop distance.
4. Ignoring Commission in Low-R:R Trades
Scalping EUR/USD at 1 lot: $7 round-turn commission. On a 10-pip target, that's $7 out of $100 profit — 7% drag. On a 50-pip target, it's $7 out of $500 — 1.4% drag. Commission matters more on tight trades. Factor it into your net expectancy, not your position size directly.
5. Different Account Currencies
If your account is in EUR but you're trading USD/JPY, the pip value in EUR is different from the pip value in USD. A $10/pip pair becomes ~€9.20/pip (depending on EUR/USD rate). Most calculators handle this automatically — but if you're calculating manually, convert the pip value to your account currency first.
Quick Reference: Position Size Formulas by Market
| Market | Formula | Example (1% risk, $10K account) |
|---|---|---|
| Forex | Lots = Risk$ ÷ (Stop pips × Pip value) | $100 ÷ (25 × $10) = 0.40 lots |
| Crypto (spot) | Coins = Risk$ ÷ (Entry − Stop) | $100 ÷ ($95K − $93K) = 0.05 BTC |
| Stocks | Shares = Risk$ ÷ (Entry − Stop) | $100 ÷ ($195 − $190) = 20 shares |
| Futures (ES) | Contracts = Risk$ ÷ (Stop pts × Point value) | $100 ÷ (5 × $50) = 0.4 → round to 0 or 1 |
| Futures (NQ) | Contracts = Risk$ ÷ (Stop pts × Point value) | $100 ÷ (20 × $20) = 0.25 → use Micro NQ |
Position Sizing for Prop Firms
Prop firm challenges add a hard constraint: the daily loss limit. This changes the math because you can't just survive the trade — you need to survive the day.
| Firm | Daily Loss Limit | Max Drawdown | If 3 Trades/Day: Max Risk Each | If 5 Trades/Day: Max Risk Each |
|---|---|---|---|---|
| FTMO ($100K) | $5,000 (5%) | $10,000 (10%) | 1.67% | 1.0% |
| TopStep ($50K) | ~$1,000 (2%) | Trailing $2,500 | 0.67% | 0.4% |
| The5%ers ($100K) | $3,000-$5,000 | $6,000-$10,000 | 1.0-1.67% | 0.6-1.0% |
| FundedNext ($100K) | $5,000 (5%) | $10,000 (10%) | 1.67% | 1.0% |
The formula: Max Risk Per Trade = Daily Loss Limit ÷ Max Trades Per Day. Then build in a 25% buffer — you never want to get within touching distance of the daily limit. So for FTMO with 3 trades/day: 5% ÷ 3 = 1.67%, buffered to ~1.25%.
For the full breakdown, see our position sizing for prop firms guide and the prop firm calculator.
Use the Position Size Calculator
Every calculation above can be done instantly with our free tool:
| Calculator | Best For |
|---|---|
| Position Size Calculator | All markets — enter account, risk %, stop loss, get exact position size |
| Lot Size Calculator | Forex-specific — handles pip values and account currency conversions |
| Risk/Reward Calculator | Check R:R before entering — what's the payoff for this risk? |
| Prop Firm Calculator | Model challenge scenarios with firm-specific rules and constraints |
Calculate before you trade, not after. The 15 seconds it takes is the cheapest risk management in trading.
Our Methodology
All formulas in this guide are standard position sizing math used across the trading industry. Pip values are for standard lots in USD-denominated accounts and fluctuate with exchange rates — the values shown are approximate as of March 2026. Prop firm rules are sourced from official websites and may change — always verify before trading. The leverage examples assume the stop loss is hit (no slippage or gaps). In live trading, actual losses can exceed calculated risk due to slippage, gaps, or platform issues.
Related Resources
- Risk management: the complete framework — daily limits, drawdown recovery, correlation
- Position sizing for prop firms — firm-specific strategies
- Win rate vs risk:reward — why R:R matters more than win rate
- How to stop overtrading — daily trade limits protect position sizing
- How to backtest a trading strategy — test your sizing rules before risking capital
Calculate Your Next Trade Right Now
Open the position size calculator. Enter your account size, 1% risk, and the stop loss distance for your most recent trade. Compare the calculator's output to what you actually traded. If there's a gap — that gap is unmanaged risk.
