Position Size Calculator
Calculate the optimal position size based on your account balance, risk tolerance, and stop loss.
Formula
Risk amount in dollars divided by the percentage distance to your stop loss gives the maximum position size that limits your loss to the desired risk amount.
Examples
- Account Balance = $10,000, Risk = 2%
- Risk Amount = $10,000 × 0.02 = $200
- Stop Distance = |$50,000 − $48,000| / $50,000 = 4%
- Position Size = $200 / 0.04 = $5,000
- Quantity = $5,000 / $50,000 = 0.1 BTC
- Account Balance = $5,000, Risk = 1%
- Risk Amount = $5,000 × 0.01 = $50
- Stop Distance = |$3,200 − $3,280| / $3,200 = 2.5%
- Position Size = $50 / 0.025 = $2,000
- Quantity = $2,000 / $3,200 = 0.625 ETH
- Account Balance = $25,000, Risk = 3%
- Risk Amount = $25,000 × 0.03 = $750
- Stop Distance = |$150 − $140| / $150 = 6.67%
- Position Size = $750 / 0.0667 = $11,244
- Quantity = $11,244 / $150 = 74.96 SOL
Key Concepts
Why Position Sizing Matters
Position sizing is the single most important risk management tool. It ensures no single trade can cause catastrophic damage to your account, regardless of the outcome.
The 1-2% Rule
Most professional traders risk 1-2% of their account per trade. This means even a streak of 10 losing trades only draws down the account by 10-20%, leaving plenty of capital to recover.
Stop Loss Distance
A tighter stop loss allows a larger position size for the same risk amount. However, tighter stops are more likely to get hit by normal price noise. Finding the right balance is key.
Risk Amount vs Position Size
Risk amount is what you lose if stopped out. Position size is the total notional value. A $5,000 position with a 2% stop distance means you risk $100, not $5,000.
Adjusting for Leverage
Leverage doesn't change the risk calculation — it only changes how much margin you need. A $10,000 position at 10× requires $1,000 margin but risks the same dollar amount at the stop.
Scaling into Positions
Instead of entering the full size at once, many traders scale in by splitting their position across 2-3 entries. This averages the entry price and can reduce risk if the first entry moves against you.
How to Calculate Position Size
Position sizing starts with a simple question: how much are you willing to lose on this trade? That dollar amount, combined with the distance from your entry to your stop loss, determines the maximum position size.
The formula works backwards from your risk tolerance. If you're willing to lose $200 and your stop is 4% away from entry, your position can be at most $5,000. This ensures that if the trade hits your stop, you lose exactly $200 — no more.
This approach is universal across all markets and timeframes. Whether you're scalping with a 0.5% stop or swing trading with a 10% stop, the math ensures consistent risk per trade.
Frequently Asked Questions
Should I use the same risk percentage for every trade?
Most traders use a consistent 1-2% risk per trade. Some adjust based on conviction — 1% for lower confidence setups and 2% for higher conviction. The key is having a maximum limit you never exceed.
Does this account for fees?
This calculator determines position size based on stop loss distance only. In practice, fees slightly increase your effective risk. For precision, subtract your expected round-trip fees from your risk amount before calculating.
What if my calculated position size is larger than my account?
That means you'd need leverage. The position size is the notional value, not the margin required. Use leverage = position size / margin to determine the leverage needed. Be cautious with high leverage as it brings liquidation risk.
How do I pick a stop loss level?
Place stops at levels where your trade thesis is invalidated — below support for longs, above resistance for shorts. Avoid arbitrary percentages. The stop should be based on market structure, not personal preference.