About the Position Size Calculator
This position size calculator tells you how many shares, coins or contracts to buy so that, if your stop-loss is hit, you lose only the amount you decided to risk. Enter your account balance, the percentage of it you are willing to lose on a single trade, your entry price and your stop price. The calculator works out the dollar risk, the risk per share and the largest whole-share position that stays inside that limit.
It is built for swing traders, day traders and anyone who wants a repeatable risk rule instead of guessing a round number of shares. Many traders risk between 0.5% and 2% of their account per trade so that a losing streak does not do lasting damage. Adding a profit target shows the reward-to-risk ratio and the potential gain, so you can skip trades where the payoff does not justify the risk.
The math works for long trades (stop below entry) and short trades (stop above entry). It assumes your stop fills at the stop price; gaps, slippage and commissions can make the real loss larger, so leave some margin.
With the default inputs, the position size is 50 shares. Change any value above to recalculate instantly.
How to use the position size calculator
- 1Enter your total account balance.
- 2Choose the percentage of the account you are willing to lose on this one trade.
- 3Enter your planned entry price and your stop-loss price.
- 4Optionally add a profit target to see the reward-to-risk ratio.
- 5Buy or short the number of shares shown — never more.
Formula and method
First the calculator converts your risk percentage into money: account size × risk % ÷ 100. It then measures the risk per share as the distance between your entry and stop prices, regardless of trade direction. Dividing the money you are willing to lose by the risk per share gives the maximum number of shares; it is rounded down so the actual risk never exceeds your limit.
If you add a profit target, the reward per share is the distance from entry to target, and the reward-to-risk ratio is reward per share ÷ risk per share. A 3:1 ratio means you stand to make three times what you risk. Commissions, spreads and slippage are not included.
- Account
- Total trading account value
- Risk %
- Percentage of the account you accept losing on this trade
- Entry
- Price you buy (or short) at
- Stop
- Stop-loss price where you exit a losing trade
Worked examples
$10,000 account, 1% risk, $2 stop
Risking 1% of $10,000 means you accept a $100 loss. The stop is $2 below the $50 entry, so $100 ÷ $2 = 50 shares, a $2,500 position. The $56 target is $6 away, giving a 3:1 reward-to-risk and $300 potential profit.
$25,000 account, 2% risk, $5.50 stop
Two percent of $25,000 is $500. With $5.50 of risk per share, 500 ÷ 5.5 = 90.9, rounded down to 90 shares, so the real risk is $495. The position is worth $10,800 (43.2% of the account) and a move to $135 would earn $1,350.
Short trade with a stop above entry
Shorting at $80 with a $83 stop risks $3 per share. Half a percent of $50,000 is $250, so you can short 83 shares ($249 real risk). If the price falls to $71 you make $9 × 83 = $747, a 3:1 payoff.
Frequently asked questions
How much should I risk per trade?+
Many professional and retail traders cap risk at 1%–2% of the account per trade. At 1%, even ten losses in a row leave you with about 90% of your capital, which keeps you in the game.
Does position size depend on where I put my stop?+
Yes. A tighter stop means less risk per share, so you can buy more shares for the same dollar risk. A wider stop requires a smaller position. Set the stop where the trade idea is wrong, then size the position.
Why is my actual risk slightly lower than my maximum risk?+
You cannot buy fractions of most shares, so the calculator rounds down to a whole number. That makes the real loss at the stop a little smaller than your limit, never larger.
Can I use this for crypto, forex or futures?+
Yes for crypto and stocks — just treat “shares” as units or coins. For forex use the pip calculator, and for futures divide the money risk by the contract’s dollar value per point instead of the price distance.
What reward-to-risk ratio is good?+
Many traders look for at least 2:1. With a 2:1 ratio you only need to win about one trade in three to break even before costs; at 1:1 you need to win more than half.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.