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.
Position size vs a stop-loss calculator
This tool answers "how big should the trade be?" given the risk you'll accept. If instead you already know your position size and just want to know the dollar loss if your stop is hit (and your risk-to-reward), use the dedicated Stop-Loss Calculator. Together they cover both sides of a trade: sizing in, and knowing your loss on the way out.
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.