Stock Position Size Calculator

Size a position so that a stop-loss triggers no more than your maximum acceptable loss.

About Stock Position Size Calculator

Position size follows from the stop distance, not from a fixed share of capital. A tight stop permits a large position at the same monetary risk, and a wide stop demands a small one. Sizing by percentage of account rather than by risk means every trade carries a different monetary risk, which is how a single position ends up dominating an account.

Formula

Stock Position Size

Shares = (account × risk per trade %) ÷ (entry price − stop price)

risk per share: Loss incurred on each share if the stop is hit
risk per trade: Share of the account you are willing to lose on one position

Worked example

With the default values below, Stock Position Size Calculator returns Shares to Buy of 100. Change any input above and every figure here is recalculated in your browser.

Inputs used

Account sizeminimum 0.01: 50,000
Maximum risk per tradeaccepts 0–100 %: 1 %
Entry priceminimum 0.01: 60
Stop-loss priceminimum 0: 55

Results

Shares to Buy: 100
Position Value: $6,000.00
Amount at Risk: $500.00
Risk per Share: $5.0000
Position as Share of the Account: 12.00%

Step by step

1Values used
2Stock Position Size
3Shares to Buy= 100
4Position Value= 6,000.00
5Amount at Risk= 500.00
6Risk per Share= 5.0000
7Position as Share of the Account= 12.00

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This is an estimate for general information and not professional financial, tax or legal advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Stock Position Size calculated?

Shares = (account × risk per trade %) ÷ (entry price − stop price) Position size follows from the stop distance, not from a fixed share of capital. A tight stop permits a large position at the same monetary risk, and a wide stop demands a small one.

Why does Stock Position Size matter?

Sizing by percentage of account rather than by risk means every trade carries a different monetary risk, which is how a single position ends up dominating an account.

What values do I need to enter?

This calculator takes 4 inputs: Account size, Maximum risk per trade, Entry price, Stop-loss price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.