Position Size Calculator
Use this tool to calculate how many shares, contracts, or coins to buy so your risk stays consistent on every trade.
Why position sizing matters more than picking the “perfect” trade
Most traders spend almost all of their energy on entries and exits, but risk control is what keeps you in the game long enough to improve. A position size calculator solves one of the biggest problems in trading: inconsistency. If one loss is tiny and the next loss is huge, your edge gets buried under avoidable volatility in your account.
Position sizing helps you define risk before entering a trade. That means your worst-case outcome is planned, not guessed. This single habit can make your trading process calmer, more repeatable, and easier to evaluate over time.
The core formula
At its simplest, position sizing is built on three numbers:
- Account size (how much capital you have)
- Risk percentage (how much you are willing to lose if stopped out)
- Risk per unit (distance from entry to stop, plus optional trading costs)
If leverage is used, available buying power can cap your size. In that case, your final size is the smaller of:
- Risk-based size
- Leverage-based maximum size
How to use this calculator correctly
1) Set account size and risk percentage
A common risk setting is 0.25% to 2% per trade. Smaller risk percentages generally create smoother equity curves and reduce emotional pressure.
2) Enter entry and stop prices
The stop price should be based on your strategy logic (market structure, volatility, or invalidation level), not just a random distance.
3) Add realistic costs
Ignoring commissions, spread, and slippage can make your backtest look better than real life. Including even a small cost estimate improves realism.
4) Choose the minimum trade increment
Different markets have different position granularity. Stocks often use whole shares, forex can use fractional lots, and crypto usually supports decimal quantities.
5) Respect leverage limits
Even if risk-based sizing suggests a larger position, margin constraints may force a smaller one. This calculator automatically checks both.
Quick examples
Example A: Stock trade
- Account: $10,000
- Risk: 1% ($100)
- Entry: $50
- Stop: $48
- Risk per share: $2
Position size is roughly 50 shares ($100 ÷ $2). If you include costs, size drops slightly to keep risk inside your cap.
Example B: Crypto trade with tighter stop
- Account: $5,000
- Risk: 0.5% ($25)
- Entry: 1.2500
- Stop: 1.2300
- Risk per unit: 0.0200
Position size is approximately 1,250 units before rounding and leverage checks. The tighter the stop, the larger the position can be for the same dollar risk.
Common mistakes this tool helps prevent
- Over-sizing after a winning streak: confidence rises faster than discipline.
- Under-sizing good setups: fear causes inconsistent execution.
- Ignoring cost drag: small costs become large over many trades.
- No pre-defined stop: without a stop, position sizing is undefined.
- Confusing conviction with risk capacity: great ideas can still fail.
Practical risk rules you can apply today
- Risk a fixed percentage per trade, not a fixed number of units.
- Lower size when market volatility increases.
- Consider total portfolio exposure, not just one position.
- Cap correlated positions (e.g., multiple tech stocks or USD pairs).
- Track expected vs. actual slippage so your size model improves over time.
Final thought
The goal of a position size calculator is not to make each trade perfect. Its job is to make your process durable. If your downside is controlled and repeatable, your edge has room to work over dozens or hundreds of trades.
Educational only, not financial advice.