Position Size Calculator
Calculate how much to buy based on your account size, risk tolerance, entry and stop-loss.
Calculator
For educational and informational purposes only — not financial, investment or tax advice. Results are estimates based on the figures you enter.
How the calculation flows
The inputs you enter feed a fixed formula to produce the result. Change any input to see how sensitive the outcome is.
Conceptual diagram
What the Position Size Calculator does
The Position Size Calculator tells you how large a trade to take so that a predetermined loss — defined as a percentage of your account — is triggered only if the price reaches your stop-loss level. It is a core risk management tool used to ensure that no single losing trade damages your account beyond the amount you have pre-approved.
The fundamental idea is straightforward: decide how much of your account you are willing to lose on this one trade (the “risk per trade”), decide where you will cut the position if you are wrong (the “stop-loss level”), and the calculator tells you the maximum position size that respects both constraints.
The formula
The result is denominated in units of the asset. Multiply by the entry price to get the dollar equivalent of the position. If the result exceeds what your exchange margin allows, size down further.
Worked example: Bitcoin position
Illustrative example — prices will differ
Account: $10,000 | Risk per trade: 2% | Entry: $65,000 | Stop-loss: $62,000
- Maximum dollar risk: $10,000 × 0.02 = $200
- Distance to stop: $65,000 − $62,000 = $3,000 per BTC
- Maximum position size: $200 ÷ $3,000 = 0.0667 BTC
- Position value: 0.0667 × $65,000 = ~$4,333
If the price falls to $62,000 and you sell at the stop, your loss is 0.0667 × $3,000 = ~$200, exactly 2% of your $10,000 account.
How risk percentage changes position size
How stop distance changes position size
| Stop distance from entry | Max position | Position value | Notes |
|---|---|---|---|
| $1,000 (1.5%) | 0.2 BTC | $13,000 | Tight stop — small move triggers exit |
| $3,000 (4.6%) | 0.067 BTC | $4,333 | Moderate stop — allows normal volatility |
| $6,500 (10%) | 0.031 BTC | $2,000 | Wide stop — larger swings tolerated |
| $13,000 (20%) | 0.015 BTC | $1,000 | Very wide — high conviction, small size |
All rows: $10,000 account, 2% risk ($200 max loss), $65,000 entry.
Worked example: altcoin with a wide stop
Higher volatility asset — illustrative
You are looking at an altcoin priced at $2.00, with a stop-loss at $1.60 (a 20% move). Your account is $5,000 and you risk 1% per trade.
- Max dollar risk: $5,000 × 0.01 = $50
- Distance to stop: $2.00 − $1.60 = $0.40 per coin
- Maximum position: $50 ÷ $0.40 = 125 coins
- Position value: 125 × $2.00 = $250
This is only 5% of the account — appropriate given the wide stop on a volatile asset. Many traders instinctively buy a round lot of coins and ignore the stop-loss arithmetic; position sizing enforces discipline before the trade is made, not after the loss.
How to use the calculator
- Enter your total account size in USD (or the equivalent).
- Enter your risk per trade as a percentage. Common values: 0.5–2% for conservative traders, 2–5% for aggressive traders. Never exceed what you are genuinely prepared to lose on a single trade.
- Enter the entry price — the price at which you plan to open the trade.
- Enter the stop-loss price — the price at which you will accept that your thesis is wrong and close the trade.
- Read the maximum position size in coins and in USD. If the dollar amount feels uncomfortably large, reduce the risk percentage or move the stop closer to entry.
Common mistakes to avoid
- Setting the stop after the position size. The correct sequence is: decide your stop first (based on the chart), then size accordingly. Deciding the size first and then placing the stop where the loss “feels right” is backwards.
- Ignoring leverage. With leveraged positions, the notional size of the trade is larger than the margin used. Always calculate position size on the full notional exposure, not just the collateral deposited.
- Using the same percentage for very different assets. A 2% risk on Bitcoin with a 5% stop-distance is very different from a 2% risk on a micro-cap altcoin with a 50% stop-distance. The position sizes will differ by 10×.
- Moving the stop to avoid a loss. Moving a stop further from entry to avoid being stopped out defeats the purpose of position sizing and converts a pre-planned risk into an open-ended one.
Common questions
What percentage should I risk per trade? A widely cited starting point is 1–2% of capital per trade. This means 50–100 consecutive losing trades would be needed to empty the account, which is extremely unlikely with a thoughtful strategy. Beginners often start at 0.5–1%.
Can I use this calculator for spot and futures trades? Yes. For spot trades, the position size is straightforward. For futures, remember to account for the leverage multiplier — a 10× leveraged position on $1,000 margin has $10,000 of notional exposure, and your stop-loss must be set relative to the full notional.
Related reading
- Glossary: Risk Management and Stop-Loss
- Guides: Understanding Crypto Risk and Volatility
- Related tools: Profit/Loss Calculator and ROI Calculator
For education only — not financial or investment advice. Position sizing does not guarantee profits or prevent all losses.