Commodity position size calculator
The risk comes first, in money. The stop converts it to a distance. The contract's unit count decides how many you can actually hold - and it rounds down, because exceeding the risk you chose is not rounding.
Why it rounds down
A budget of 1.7 contracts is a position of 1. Rounding up to 2 would carry more risk than the number you began by choosing, and a sizing tool that quietly does that has answered a different question. The gap between the risk budget and the risk actually carried at the whole size is shown, because knowing it is the difference between sizing and guessing.
When the answer is zero
Commodity contracts are large - 1,000 barrels, 5,000 bushels - and a realistic stop on one contract can exceed a small account's entire risk budget. Zero is then the correct size, not a malfunction. The choices from there are a wrapper that slices the contract smaller, a wider risk budget chosen deliberately rather than by rounding, or standing aside - and this page will not pick one for you.
The two unit traps
The stop distance is in the quoted price's own units: dollars per barrel for crude, dollars per troy ounce for gold. Grains quote in cents per bushel, so a 25-cent wheat stop is 0.25 here, never 25. And the unit count comes from the exchange's contract specification, not from memory - the worked figures on this site are checked against exactly that source.
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