Position Size Calculator

Position size calculator

Enter your account size, how much of it you're willing to risk, and where your stop is. You'll get the number of shares or contracts that keeps a losing trade inside that limit.

Free

No sign-up

Runs in your browser

Instrument

Stock

Option

Future

Account size

Risk per trade

The share of your account you're willing to lose if the stop is hit.

Entry price

Stop loss

Below the entry for a long, above it for a short.

Position size

125 shares

Long · $2.00 risk per share

Risk budget

$250.00

Actual risk

$250.00

Position value

$6,250.00

Of account

25.0%

If the stop is hit you lose about $250.00 (1.00% of the account), before slippage and fees.

Stop calculating by hand

SetMetric is a free trading journal that does this math for every trade you take — position risk, R-multiples, win rate, expectancy and drawdown — and shows you which setups, times and habits make or lose you money.

How position size is calculated

Position size = (account size × risk per trade %) ÷ (risk per share × multiplier).

Risk per share is the distance between your entry and your stop loss. With a $25,000 account, 1% risk ($250), an entry at $50 and a stop at $48, you risk $2 a share, so you can buy 125 shares. If the stop is hit you lose about $250, before slippage and fees.

For options, use the option's price for entry and stop and a multiplier of 100 (one contract covers 100 shares). For futures, use the contract's dollar value per point as the multiplier — for example 50 for the E-mini S&P 500 (ES) or 5 for the Micro (MES).

How much should you risk per trade?

Many traders risk between 0.5% and 2% of their account on a single trade. The smaller the risk, the longer you can survive a losing streak: at 1% risk, ten losses in a row costs you about 10% of the account; at 5% risk it costs about 40%.

Whatever you choose, keep it consistent. Changing size based on how confident you feel is one of the most common ways traders turn a winning strategy into a losing one.

Common position sizing mistakes

•

Setting the size first and then placing the stop wherever it fits — the stop should come from the chart, the size from the stop.

•

Forgetting that a gap or fast move can fill you beyond your stop, so the real loss can be bigger than planned.

•

Ignoring the position's total value: a tight stop can produce a position larger than your buying power.

•

Not checking afterwards whether your actual losses matched your planned risk.

Frequently asked questions

Position size equals your dollar risk (account size times risk percent) divided by your risk per share (the distance from entry to stop, times the contract multiplier for options or futures). The result is rounded down to whole shares or contracts.

It depends on your stop, not the account alone. Risking 1% ($100) with a $0.50 stop allows 200 shares; with a $2 stop it allows 50 shares. Enter your own entry and stop in the calculator above.

Yes. Put the stop above the entry and the calculator treats it as a short. The size formula is the same because it only uses the distance between entry and stop.

Enter the option or futures price for entry and stop and set the multiplier: 100 for standard equity options, or the contract's point value for futures (for example 50 for ES, 5 for MES, 20 for NQ, 2 for MNQ).

Shares and contracts are whole numbers, so the size is rounded down. The calculator shows the risk at the rounded size so you never go over your limit.