You are planning how many shares fit both a maximum loss assumption and the capital available for the position.
Position Size Calculator for Stocks
Estimate shares from account risk, entry price, stop price, available capital, and optional transaction fees.
Start here
Choose account-percentage risk or enter a fixed risk budget.
Browser-first
Your account, price, and risk inputs are calculated locally in your browser and are not uploaded to a server.
Useful for
Convert a percentage risk limit into a share count
Position size100 sharesLimited by risk budget
Position value$5,000.0020.0% of entered account balance
Planned stop loss$250.00Budget: $250.00
Risk per share$2.50Price distance plus modeled variable fees
Entry fee estimate: $0.00
Modeled exit fee at the stop: $0.00.
Use the smaller limit
The result respects both the risk formula and the entered capital available.
Stops are not guaranteed execution prices. Gaps, slippage, fees, borrow costs, and order failures can make the actual loss larger.
Quick answer
Estimate share size from entry, stop, and risk
Enter an account-based or fixed risk budget, entry price, stop price, available capital, and optional fees to estimate a share count for a long or short trade plan.
Stops do not guarantee execution price, and gaps, slippage, liquidity, fees, borrow terms, and leverage can make actual loss larger.
Stock Average Cost: Calculate weighted average purchase cost, total shares, total invested amount, and optional transaction fees across multiple stock purchases.
About this tool
Estimate shares from account risk, entry price, stop price, available capital, and optional transaction fees.
Your account, price, and risk inputs are calculated locally in your browser and are not uploaded to a server.
Reminder
This is an educational planning estimate, not investment advice or an order recommendation. Stops can gap or fail to execute at the selected price, slippage and fees may be higher, and losses can exceed the planned amount.
How to use it
- Choose account-percentage risk or enter a fixed risk budget.
- Enter the entry price, stop price, available capital, direction, and optional fees.
- Calculate the risk-based shares and review the capital cap and loss estimate.
Common use cases
- Convert a percentage risk limit into a share count
- Size a long or short stock trade around a stop
- Check whether the risk-sized position exceeds available capital
- Compare whole-share and fractional-share estimates
Risk-Based Position Size Formula
Start with the amount you are prepared to lose if the stop is reached. Divide that risk budget by the planned loss per share, then compare the result with the shares affordable from available capital.
| Example input | Value | Calculation |
|---|---|---|
| Account balance and risk | $25,000 at 1% | $250 risk budget |
| Entry and stop | $50 entry, $47.50 stop | $2.50 risk per share |
| Risk-based size | $250 ÷ $2.50 | 100 shares before fees and capital cap |
Why Actual Loss Can Exceed Planned Risk
A stop price is a planning input, not a guaranteed execution price. Fast markets, overnight gaps, low liquidity, order type, borrow constraints, and platform outages can all change the result.
- Use the same currency for balance, prices, capital, and fees.
- Include a conservative cost allowance when commissions or slippage are material.
- Short positions add borrow, margin, recall, and theoretically unlimited-loss risks that the share-count formula does not model.
FAQ
What is the basic position-size formula?
Risk-based shares equal the money risk budget divided by risk per share. Risk per share is the absolute distance between entry and stop, plus any included per-share cost estimate.
Why is the result capped by available capital?
A risk formula can produce a position that costs more cash than is available. The calculator shows the lower of the risk-based and affordability limits.
Can I calculate a short position?
Yes. Choose short and place the stop above the entry price. This does not model borrow availability, margin rules, unlimited loss risk, or forced liquidation.
Will my loss equal the estimate?
Not necessarily. Price gaps, slippage, partial fills, commissions, taxes, and execution failures can make the actual loss larger.