Position size calculator
Work out how many shares to buy from your account size, the percent you are willing to risk, your entry and your stop. Nothing is stored and nothing is sent anywhere.
Position size is the money you are willing to lose divided by the distance between your entry and your stop. Risking 1% of a $25,000 account is $250; with an entry of $186 and a stop of $184 you are risking $2 a share, so you buy 125 shares. The calculator below does that arithmetic and rounds down.
Work out your size
- Shares to buy
- 125
- You are risking
- $250.00
- Risk per share
- $2.00
- Position value
- $23,250.00
- Share of account
- 93.0%
- Reward to risk
- 3.00R
- If the target hits
- $750.00
Share counts are rounded down so your real risk never exceeds the budget. Commissions, slippage and gaps past your stop are not included.
How do you calculate position size?
Divide the money you are willing to lose by the distance between your entry and your stop. If you risk 1% of a $25,000 account, that is $250. With an entry of $186 and a stop of $184, the risk per share is $2, so you buy 125 shares.
How much should I risk per trade?
Most position-sizing writing lands between a half and two percent of account equity on a single trade. The number matters less than using the same one every time — consistent sizing is what makes a run of losses survivable and your results comparable.
Does this calculator store my numbers?
No. The maths runs in your browser and nothing is sent anywhere, saved, or logged. There is no signup and no account. Close the tab and the numbers are gone.
Does it work for short trades?
Yes. Put your stop above your entry and it sizes the short the same way, using the distance between the two. A target below the entry gives you the R multiple.
Why does position sizing matter more than picking winners?
Because size decides how long you survive. A trader who is right half the time and sizes the same way every trade compounds; a trader who is right most of the time and sizes up on conviction can lose it all in one position. Sizing is the part you fully control.
The number you choose matters less than choosing one and keeping it. Sizing consistently is what makes a losing streak survivable, and it is what makes your own results comparable to each other — if every trade risks the same amount, your expectancy and R multiples actually mean something.
That is also the argument for writing the size down. A journal that records what you risked, and why, is the only way to notice that your losses cluster on the trades where you sized up.
Want these numbers kept for you, trade after trade? sizeforzero is a free trading journal that tracks your risk, your equity curve and your notes — and reads them back to you.
Start free — no card