Position size calculator
Enter your account size, how much you're willing to risk, your entry and your stop loss. The calculator tells you how many shares to buy so that, if your stop is hit, you lose exactly the amount you chose and no more.
Shares to buy
40
Long trade
Money at risk
$100.00
Risk per share
$2.50
5.0% from entry
Position value
$2,000.00
Share of account
20%
How it works
- 1Money at risk = account size × risk %. A $10,000 account risking 1% puts $100 on the line.
- 2Risk per share = entry − stop loss. Buying at $50 with a stop at $47.50 risks $2.50 a share.
- 3Shares = money at risk ÷ risk per share. $100 ÷ $2.50 = 40 shares, a $2,000 position.
- 4Notice the position is 20% of the account, but the risk is only 1%. The stop, not the position value, decides how much you can lose (apart from overnight gaps).
Questions people ask
How do you calculate position size?
Multiply your account size by the percent you're willing to risk, then divide by the distance between your entry and your stop loss. That gives the number of shares.
How much should I risk per trade?
Many traders risk 0.5% to 2% of their account on a single trade. At 1%, ten losses in a row still leave about 90% of your account.
Does this work for crypto and short trades?
Yes. For crypto, the result is the number of coins (fractions are fine; the calculator rounds down to whole units). For a short trade, put the stop above the entry.
Why is my position bigger than my risk?
Because you only lose the distance down to your stop, not the whole position. A $2,000 position with a stop 5% below entry risks about $100.
Let Boo plan the trade for you
Upload a screenshot of any chart or type a ticker. Boo reads it and hands you the entry, stop loss, target and position size in seconds. Your first full plan is free.