How do I calculate position size?

Multiply your account balance by your risk percentage to get your dollar risk amount. Divide that by the dollar risk per unit (the difference between your entry and stop loss price, multiplied by your contract multiplier). The result, rounded down, is the number of shares, coins, or contracts to trade.

What is a contract multiplier?

The contract multiplier converts a price move into a dollar amount. For stocks and crypto, this is 1 — a $1 move equals $1 per share or coin. For futures, each contract represents a fixed dollar value per point of price movement (for example, the ES e-mini S&P 500 future has a multiplier of $50 per point).

Why should position size depend on my stop loss distance?

If you use a fixed number of shares or contracts regardless of your stop distance, a wider stop means a bigger dollar loss for the same percentage risk. Calculating position size from your stop distance keeps your risk per trade constant in dollar terms, no matter how tight or wide your stop loss is.

Is this calculator useful for prop firm challenges?

Yes. Prop firms enforce strict daily and overall drawdown limits, so consistently risking a fixed percentage per trade — rather than a fixed number of shares or contracts — is essential to avoid an unexpected large loss that breaches those limits.

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Free Tool

Position Size Calculator

Calculate exactly how many shares, coins, or contracts to trade based on your account size, risk percentage, and stop loss.

Configure

Account balance ($)

Risk per trade (%)

Entry price

Stop loss price

Contract multiplier

Use 1 for stocks/crypto. For futures, enter the $ value of a $1 price move per contract (e.g. 50 for ES e-mini).

Result

Position size

50 units

Risk amount

$100.00

Risk per unit

$2.0000

Total position value

$5,000

% of account

50.0%

Track this automatically in your trading journal — no more manual math.

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Size vs stop distance

1x = your current stop

As your stop distance widens, position size decreases to keep your dollar risk constant. The dashed line marks your current stop setting.

How to use the position size calculator

Position sizing is the link between your trade idea and your risk management plan. Enter your account balance, the percentage you're willing to risk on this trade, and your entry and stop loss prices. The calculator works out your dollar risk per unit and divides your total risk budget by that figure to give you the exact position size.

This calculator works across stocks, crypto, and futures. For stocks and crypto, leave the contract multiplier at 1. For futures, enter the dollar value of a one-point move for your specific contract so the position size accounts for leverage correctly.

Sizing your position from your stop distance — rather than using a fixed number of shares or contracts every time — keeps your dollar risk consistent across trades with different stop distances, which is essential for staying within prop firm drawdown limits.