Free stock risk tool

Stock position size calculator

Estimate whole shares from a defined entry, stop, account balance, and risk percentage. For long positions, the result also respects your available cash.

Free to useNo signup requiredTransparent formula

Quick answer

How do I calculate stock position size?

Divide the money you plan to risk by the absolute distance between entry and stop, then round down to whole shares. For an unleveraged long position, also cap shares by available cash divided by entry price.

Calculate shares from a planned stop

Choose an account risk limit before calculating a whole-share quantity.

Account balance ($)Risk per trade (%)Entry price ($)Stop price ($)Available cash ($)

Risk budget

$100

Risk per share

Maximum whole shares

Planned loss at stop

$100

The risk formula permits 50 shares; available cash permits 200. This tool uses the lower count. Position value at entry: $2,500.

A stop may fill beyond its trigger price. Fees, slippage, taxes, corporate actions, borrow costs, and broker rules are excluded. Fractional shares and leverage are not assumed.

The risk-based share formula

Whole shares = floor(risk budget ÷ price risk per share). A $10,000 account risking 1% has a $100 budget. With a $50 long entry and a $48 stop, risk is $2 per share, so the risk formula allows 50 shares.

Check cash as well as stop risk

A long trade can fit a chosen stop-risk budget while requiring more cash than is available. For a long position, this tool also limits quantity to floor(available cash ÷ entry price). It assumes no leverage or fractional shares.

Short positions need broker checks

For a short, the stop is above entry. The displayed count comes from the stop-risk formula, but it does not verify whether shares are available to borrow or how much margin the broker requires. Losses on a short can exceed the planned amount.

Evaluate the target separately

Quantity answers how much is at risk if a planned stop is reached. It says nothing about whether the proposed target is realistic. Check the entry, stop, and target with the risk reward calculator, then record the plan before the outcome.

Frequently asked questions

Questions about this free tool

Why is the long share count lower than risk-based shares?

Available cash may not buy every share allowed by the stop-risk formula. This tool uses the lower of risk-based and cash-based share counts for a long position.

Does the calculator account for short-sale margin?

No. The short calculation is only stop-based risk arithmetic. Confirm borrow availability, margin, and broker rules independently.

Does a stop guarantee the displayed maximum loss?

No. Stops can fill beyond the intended price during a gap or fast market, and trading costs add to losses.

Plan the trade before risking capital

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