Trading Risk Calculator and Position Size Tool
Decide how many dollars one trade may lose, enter the entry and the stop, and the calculator returns how many whole shares fit that risk — plus the position value and, with a target, the reward-to-risk. Arithmetic only, not advice.
How the quantity is calculated
The distance between the entry and the stop is the risk per share. The amount you decided to risk, divided by that distance, is the quantity — rounded down to a whole share, which is why the actual risk is equal to or smaller than the amount you set. A stop below the entry means a long; a stop above it means a short.
What the calculator does not do
- It does not decide how much to risk — that number is yours
- It does not know your account size
- It ignores commissions, slippage and opening gaps
- Whole shares only, no fractional quantities
- Stocks and ETFs, not options
From the numbers to a plan
With a symbol, the button under the result opens a trade-plan draft that carries the entry, stop, target and risk. On the chart the stop and target become lines, the plan is saved, and when the trade closes the journal compares the result with the plan.
FAQ
How is position size calculated from a fixed dollar risk?
Risk per share is the distance from the entry to the stop. Dividing the dollars you decided to risk by that distance gives the number of shares; the calculator rounds it down to a whole share.
Why is the quantity rounded down?
A fraction of a share cannot be bought as a whole share, and rounding up would risk more than the amount you set. Rounding down keeps the actual risk at or below that amount; the calculator shows the actual figure.
What is the difference between risk per share and risk per trade?
Risk per share is the price distance to the stop, in dollars per share. Risk per trade is the total you decided to lose if the stop is hit; the quantity is what connects the two.
What is reward-to-risk and how is it calculated here?
It compares the distance from the entry to the target with the distance from the entry to the stop. A target 10 above an entry with a stop 5 below reads 1 : 2.0. It is shown only when the target is on the opposite side of the stop.
How does the calculator handle a short?
A stop above the entry is read as a short. The risk per share is still the distance to the stop, and a valid target must be below the entry; everything else is calculated the same way.