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Position size calculator

How many shares should this trade be? Enter your account size, the percentage you are willing to risk, your entry and your stop. The answer updates as you type. Nothing to sign up for.

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%
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Position size
41 shares
Risk per share
$2.40
Money at risk
$98.40
Position value
$1,935.20
Share of account
19.35%

This calculator does arithmetic on the numbers you type in. It does not know your account, it does not see the market, and it is not advice. The 1% default is a widely used convention, not a recommendation — the right figure for you depends on circumstances this page cannot see.

What this calculates

Position sizing answers a narrow question: given how much you are prepared to lose on a trade, and how far away you have placed your stop, how large can the position be? It is the step that connects a risk decision to an order quantity.

It is worth separating two things that are easy to confuse. Your stop sets your risk per share — the distance between where you get in and where you get out. Your position size sets how many shares carry that risk. They are different levers, and moving one without thinking about the other is how a carefully chosen stop ends up attached to a position far larger than intended.

The formula

The whole calculation is two divisions:

risk per share = | entry price − stop price |

money at risk  = account size × ( risk % ÷ 100 )

position size  = money at risk ÷ risk per share

In stock mode the final figure is rounded down to a whole share. Rounding down keeps the position at or below the risk you asked for; rounding up would quietly exceed it.

A worked example

Suppose the account holds $10,000 and you are risking 1% of it. You plan to buy at $47.20 and exit if the price reaches $44.80.

  • Risk per share is $47.20 − $44.80 = $2.40
  • Money at risk is $10,000 × 1% = $100
  • $100 ÷ $2.40 = 41.67, rounded down to 41 shares
  • Those 41 shares are worth $1,935.20, or about 19% of the account
  • The actual money at risk is 41 × $2.40 = $98.40

Note the gap between the two percentages. Risking 1% of the account does not mean committing 1% of it — here it means putting roughly a fifth of the balance into the position, while the amount that can be lost stays near $100. Those figures are the calculator's defaults, so the page loads showing exactly this example.

What the inputs mean

Account size
The balance you are sizing against. Some people use the whole account and some use only the portion allocated to active trading; the calculator uses whatever figure you give it.
Risk per trade
The share of that balance you are prepared to lose if the trade reaches your stop, expressed as a percentage.
Entry price
The price you expect to get filled at. A market order in a fast-moving name may fill somewhere else.
Stop price
The price at which you would exit. It can sit above your entry — the calculator will size a short position the same way, since only the distance matters.

Frequently asked questions

What percentage should I risk per trade?

There is no figure this page can give you, because the answer depends on your income, your obligations, your time horizon and your tolerance for a losing streak — none of which a calculator can see. The 1% default here is simply the most commonly cited convention in trading literature; it is popular because it takes a long run of losses to do serious damage to an account at that size. It is a starting point for your own thinking, not a recommendation.

Is the money at risk figure a guarantee of my maximum loss?

No, and this is the most important limitation to understand. The figure assumes you exit at exactly your stop price. In practice a stop can fill worse than the price you set — during fast moves, at the open, or when a stock gaps overnight past your level and the first available price is well below it. Illiquid names and thin pre-market or after-hours sessions make this worse. Treat the number as the risk you planned, not the loss you are promised.

Does this work the same way for crypto?

The arithmetic is identical. The only difference is that crypto trades in fractional units rather than whole shares, so switching the calculator to Crypto stops rounding your size down to a whole number. Bear in mind that crypto trades around the clock, so a stop can be reached at three in the morning while you are asleep.

Why did I get fewer shares than the raw division suggests?

In stock mode the result is rounded down to a whole share, because most brokers will not fill a partial one. Rounding down rather than up means the position stays at or under the risk you specified instead of slightly over it. If your broker supports fractional shares, the Crypto setting will show you the unrounded size.

What happens if my stop is very close to my entry?

A tighter stop means a smaller risk per share, so the same dollar risk buys a larger position. That is arithmetic, not a free lunch: a tighter stop is also easier for ordinary intraday noise to reach, so the trade is more likely to be closed for a loss that the wider stop would have survived. The position size calculation cannot tell you whether a given stop is placed sensibly.

Related

Once you hold the shares, writing a call against them caps the upside in exchange for premium — the covered call calculator works out what that pays and where it breaks even. Both live on the tools page.

Sizing that happens without you

Working the arithmetic out by hand is fine when you are placing one trade. It is harder when the setup appears while you are at work. Clock Out Capital exists for that gap: bots apply rules like these on the broker account you already have, so the sizing happens whether or not you are at a screen. You can see what that costs on the pricing page, or look at the other free tools.

Trading involves risk, including the risk of losing more than you planned. This page is educational and is not financial advice, a recommendation, or an offer. Nothing here predicts a result. See the full risk disclosure.