Position size calculator
Your stop and your risk decide the size. Enter your own numbers — nothing is stored and nothing is sent anywhere.
Futures position size
Needed for the percentage figures.
Prop account — how much room is left
With intraday trailing: the highest unrealised peak.
At several firms the threshold stops climbing once it reaches the starting balance, or exceeds it by a small amount.
Position size within the remaining room
Fill in the prop account section above, and the remaining room becomes available here and as a button next to the risk field.
Forex position size
For example EURUSD. The pip size is 0.01 for pairs containing JPY, 0.0001 otherwise.
Needed to work out the pip value. Enter the current rate of the pair.
Needed for the percentage figures.
Explanations
What R means
R is the amount you lose if the trade goes against you and your stop is hit. Not the size of your account, not the number of contracts — just the loss. If your stop costs you 200 dollars, that is one R.
Everything else is measured against it. A target twice as far away as your stop is 2R. A trade that goes nowhere and stops you out is minus one R. Over fifty trades you can add them up, and the total tells you whether the approach works, independently of how big your account was at the time.
This matters because win rate on its own says nothing. Thirty percent with a 3R target adds up. Sixty percent with a half-R target does not. Anyone quoting a win rate without the R is leaving out the half of the equation that decides whether there is money in it.
Why the stop decides the size
The order most people use is backwards. They decide how many contracts to trade, enter, and then look for somewhere to put the stop. That makes the risk whatever the chart happens to allow.
The other way round: decide what the trade is worth risking, find where the stop belongs on the chart, and let those two numbers determine the size. The stop goes where the idea is wrong — not where the loss becomes comfortable. If that distance means one contract instead of four, it means one contract.
A wide stop is not a problem. A wide stop with the same position size as a narrow one is.
Why percentages do not work on a prop account
On your own account, risking one percent means one percent of what you have. On a prop account, the number on the label is not what you have. What you have is the distance between your balance and the threshold that closes the account.
Worse, on a trailing drawdown that distance moves. It rises with your equity and never comes back down. So after a good day you are not further from the floor — you are closer to it in relative terms, because the floor came up with you while your balance can still fall back.
That is the part that catches people. A trader up two thousand on a fifty thousand account feels like they have more room than on day one. Often they have less. The calculator above asks for your peak balance precisely because that number, not the account label, decides how much you can lose today.
What this calculator cannot know
It does not know your firm's rules. It asks you for them because published summaries of prop firm rules contradict each other, the programs change, and the same firm runs several account types with different behaviour. Read your own account page and type in what you find there.
It does not know your commission or your slippage. Both come out of the same room you are measuring, and on a tight stop they are not small.
It does not know whether the stop you entered is in a sensible place. It will size a position around a stop that makes no sense just as happily as around one that does.
And it does not know whether the trade is worth taking. That is not a calculation.
Limits
- No commission or slippage is included. Both reduce your real room.
- The contract specifications are exchange-defined and stable, but check them with your broker.
- Prop firm rules differ by firm, by account type and by date, and public summaries of them contradict each other. Enter your own numbers from your own account — do not rely on anything you read about your firm elsewhere, including here.
- This is a calculator, not advice.