Position Size Calculator

Position sizing is the most important number in any trade, and it is the one beginners most often guess. This calculator works it out from four inputs: how much money is in your account, what percentage of it you are willing to lose if the trade fails, where you will enter and where your stop loss sits. It returns the number of units to buy or sell so that hitting your stop costs exactly the amount you chose, no more. It works for shares, crypto, or any instrument priced per unit. For futures, use the Futures Tick Value Calculator to convert ticks into money first.

Calculator#

How it works#

Money at risk = Account size × Risk per trade %
Position size = Money at risk / |Entry price - Stop price|

The distance between entry and stop is your risk per unit. Dividing the money you are willing to lose by that distance gives the size at which a stopped out trade costs exactly your chosen amount. The same formula works for long and short trades, because only the distance matters. See Position Sizing and Fixed Percentage vs Fixed Dollar Risk.

Choosing your risk percentage#

With 1% risk, ten losing trades in a row cost about 9.6% of the account. With 5% risk, the same streak costs about 40%. Losing streaks happen even to good strategies. See Losing and Winning Streaks and Risk of Ruin.

Things the calculator does not include#

1. Slippage and gaps: stops can fill worse than planned, especially overnight or in fast markets. See Slippage and Price Gaps and How to Trade Them.
2. Fees and commissions, which add to the real loss. See Commissions and Fees.
3. Leverage limits: a tight stop can produce a position larger than your buying power. Check the "share of account" result. See Margin and Leverage Calculator.
4. Correlation: several positions in related assets add up to more risk. See Portfolio Heat.
5. Lot size rules: round down to the units your broker allows, such as whole shares or minimum crypto increments.

Using position sizing every trade#

Make the calculation part of your pre trade routine: set the stop where the trade idea is proven wrong, then let the calculator decide size. Never move the stop to fit a size you wanted. See Pre-Trade Checklist and Building a Trading Plan.

Frequently asked questions#

How do I calculate position size?#

Multiply your account size by the percentage you are willing to risk, then divide by the distance between your entry and stop loss price.

What percentage of my account should I risk per trade?#

Many traders risk between 0.5% and 2% per trade; smaller percentages keep losing streaks survivable.

Does position sizing work for short trades?#

Yes. The formula uses the distance between entry and stop, so it works the same for long and short positions.

Next, check whether a trade is worth taking with the Risk/Reward Calculator.