Grizzly Bulls

Stock Position Size Calculator

Translate an account-level loss budget and stop price into a whole-share long or short position. Add an optional portfolio-size cap and target price to see which constraint actually binds and what the entered reward/risk looks like.

Inputs

Use the account value whose loss budget and position-size cap you want to model.
Enter a percentage such as 0.5, 1, or 2. The calculator does not recommend a risk level.
For a long position, the stop must be below the entry.
Used only for entered reward/risk and simplified break-even win-rate math.
Leave blank to size only from stop risk. The cap is limited to 100% because this calculator does not model leverage or margin.

Position-size result

$500.00Maximum dollar risk budget
$5.00Price risk per share to the entered stop
100Maximum whole shares
Both limitsBinding sizing constraint
$10,000.00Modeled position notional
20%Position notional as share of account
$500.00Modeled loss if filled at the entered stop
1%Modeled account risk actually used
2REntered target reward/risk
$1,000.00Modeled gain at entered target
33.33%Simplified break-even win rate at that reward/risk

The entered stop is 5% from entry. Whole-share rounding leaves $0.00 of the entered loss budget unused. The minimum account size for one share under the entered risk percentage is $500.00 before any position-size cap.

How the position size is calculated

The calculator starts with the amount of account equity you are willing to put at risk if the position reaches the entered stop. It then floors the share count so whole-share sizing does not exceed that loss budget. If you also enter a maximum position percentage, the smaller of the stop-risk size and notional-cap size wins.

Risk budget = account equity × risk limit %
Risk per share = |entry price − stop price|
Risk-limited shares = floor(risk budget ÷ risk per share)
Position-cap shares = floor(maximum position notional ÷ entry price)
Final shares = smaller applicable whole-share limit

With the default inputs, a $50,000 account at a 1% loss budget has $500 of modeled risk. A $100 entry and $95 stop create $5 of price risk per share, which permits 100 shares. A 20% position cap also permits 100 shares, so both constraints bind.

Reward/risk is an input check, not a forecast

If you enter a target, the calculator compares the target distance with the stop distance. A $10 target gain against $5 of stop risk is 2R. The displayed break-even win rate is the simplified two-outcome arithmetic implied by that entered reward/risk ratio; it is not an estimate of how often the target will be reached.

The calculator does not estimate expected return, win probability, gap risk, borrow cost, dividends on short positions, taxes, or changing position size after entry. For sample uncertainty around an observed win rate, use the Backtest Win Rate Confidence tool. For sequence risk, use the Trading Losing Streak Calculator.

A stop price does not guarantee the modeled loss

The loss figure assumes the full position can exit at the exact entered stop price. Real trades can gap through a stop, slip during fast markets, incur commissions or fees, or face liquidity and short-borrow constraints. A stop order is an execution instruction, not a guaranteed loss cap.

This page sizes stocks from user-entered prices only. It does not choose a stock, entry, stop, target, direction, risk percentage, or maximum position size. If you are sizing ES, MES, NQ, or MNQ instead, use the Futures Position Size Calculator, which applies the same account-risk-budget logic to contract multipliers and tick sizes.