How to size a position by risk
Decide how much of your account you're willing to lose on one trade (the risk %), then let your stop-loss set the size. Enter your account size, risk percent, entry price, and stop-loss. The calculator returns the exact position size so that if your stop is hit, you lose only the amount you chose — no more. For a long trade your stop sits below your entry; for a short, above. Only the distance between them matters.
The formula
Risk $ = Account × risk% · Position size = Risk $ ÷ |Entry − Stop| · Position value = Size × Entry
Worked example
A $10,000 account, risking 1%, entry $30,000, stop-loss $28,500:
- Amount at risk: $10,000 × 1% = $100
- Price risk per coin: $30,000 − $28,500 = $1,500
- Position size: $100 ÷ $1,500 = ≈ 0.0667 coins
- Position value at entry: ≈ $2,000
Why risk-based sizing matters
Most accounts blow up not from bad picks but from oversized positions. Fixing your risk per trade — many traders use 1–2% — means a string of losses barely dents your capital, so you stay in the game. The stop-loss isn't just an exit; combined with your risk budget it tells you exactly how big the trade should be.
Common mistakes to avoid
Setting the stop too tight just to trade bigger — give the price room to breathe. Ignoring fees and slippage, which add to the real loss. Risking far more than 1–2% per trade. Moving the stop further away after entry, which quietly breaks the whole calculation.
Frequently asked questions
Account $10k, risk 1%, entry $30k, stop $28.5k — what size?
You risk $100; the stop is $1,500 away, so size ≈ 0.0667 coins, a ~$2,000 position.
What is the 1% rule?
Risk no more than 1% of your account on a single trade so one loss can't badly hurt you.
Does it work for stocks and forex?
Yes — use the entry and stop prices for any instrument; the maths is the same.
Where should I put my stop?
At a price that invalidates your trade idea — not at an arbitrary level chosen to allow a bigger size.
Is my data saved?
No. Everything runs in your browser; nothing is uploaded.