Position Size Calculator
Work out how many shares or contracts to take so a loss costs exactly what you decided it would. There is no signup, and nothing you type leaves your browser.
- Risk budget
- 500.00
- At risk on this trade
- 500.00
- Risk per unit
- 2.50
- Position cost
- 37,880.00
- Share of account
- 75.8%
- Direction
- Long
How the math works
Two steps, and the second one is the part traders skip. First, decide what a loss is allowed to cost: account size times risk percent. On a 50,000 account risking 1%, that is 500. Second, divide that budget by the distance from your entry to your stop. An entry at 189.40 with a stop at 186.90 puts 2.50 at risk per share, so 500 divided by 2.50 is 200 shares.
Options work the same way with one extra step. One standard contract controls 100 shares, so a 1.00 move against you costs 100 per contract, not 1.00. The calculator applies that multiplier for you when you switch the instrument.
Sizes are always rounded down. If 33.4 shares fit the budget, taking 34 breaks the rule you just set, which defeats the point of setting it.
Sizing right is easy. Doing it every time is the hard part.
VEXA imports your fills from 21+ brokers and flags the trades where your size drifted from your own rule, so you find out on the same day instead of at the end of a bad month.
See plansQuestions
How do you calculate position size?
Multiply your account size by the percent you are willing to risk to get a dollar risk budget. Divide that budget by the distance between your entry and your stop. For options, multiply the stop distance by 100 first, because one standard contract covers 100 shares.
How much should I risk per trade?
Most position-sizing rules land between 0.5% and 2% of account equity per trade. The number matters less than applying the same number every time, because consistent sizing is what makes a string of losses survivable.
Why does the calculator round the size down?
Rounding up would breach the risk budget you just typed in. If 33.4 shares fit your budget, 34 shares risk more than you allowed, so the calculator gives you 33.
Does this work for futures and forex?
Yes, if you set the contract multiplier to the value of a one-point move for your instrument. Leave it at 1 for shares, use 100 for standard equity options.