Tools
Position size calculator
This calculator answers a narrow question: if you are willing to lose a stated fraction of an account between an entry and a stop, how many units is that? It does not know whether the stop will fill, or whether the trade should exist.
How the calculation works
Risk amount is account size multiplied by the risk percent. Distance is the absolute difference between entry and stop. Units equal risk amount divided by distance, when distance is above zero. The result is a raw quantity. You still have to round to the lot, contract or share size the venue allows.
Assumptions
- The stop fills at the stop price, which is often false in a gap.
- One unit loses exactly the distance, with no multiplier hidden in the contract.
- Account size is the capital you are actually using, in one currency.
- Costs, slippage and currency conversion are excluded.
A worked example
On an account of 20,000, a 1% risk budget is 200. If the entry is 50 and the stop is 48, the distance is 2, so the raw size is 100 units. A gap through 48 means the loss is larger than 200 and the calculator will not have warned you with a number, only with this paragraph.
Limitations
Futures and options have multipliers. A unit is not always one share. Do not type a premium into a field designed for a price stop and expect an options size. There is a separate options calculator for a long call or put.
Change one input at a time if a result looks surprising. The arithmetic is only as careful as the numbers you type, and it does not know your broker’s contract size.
Illustrative result
Round to a tradable size yourself. A gap through the stop makes the loss larger than the risk amount.
Related
Sources and review
Last reviewed: 2026-10-13. Next review due 2027-04-13. Status: editorial review of this page, not a live verification of every third-party fee.
Author: WiT Markets Editorial, Editorial desk. The WiT Markets editorial desk writes explanatory pages, comparison context and research notes. It separates sourced facts from items that are not confirmed, and it does not provide personal recommendations.
Reviewed by: WiT Markets Research Review.
Primary and regulatory sources
- Investor.gov — checked 2026-10-13