News and Updates

USPTO rejects correct use of SI units

A recently filed certificate of correction request was denied in part. The USPTO provided the following explanation for the denial:

Period is missing after C (Celsius)/F (Fahrenheit) [...]. Also the degree sign should be flush the proceeding number not the "C". [...] This does not conform to our data capture style rules from the USPTO.

Looking at it a little closer, the USPTO did reformat the specification throughout the published patent:

Applicant’s specification
USPTO published patent

Note that “40 °C” was changed to “40° C.” The USPTO moved the degree symbol to the number, separated “°” and “C” with a space, and added a period after “C.” Sadly, the USPTO practice is in direct contrast with the correct use of the unit “degree Celsius” as established in The International System of Units (SI). The SI includes rules regarding the writing of unit symbols and names. Section 5.4.3 of the system defines that “the numerical value always precedes the unit and a space is always used to separate the unit from the number.” With respect to temperature the rule is explicit: “This rule means that the symbol °C for the degree Celsius is preceded by a space when one expresses values of Celsius temperature t.”

So why do the USPTO formatting guidelines directly contradict the SI system even though the United States is a member of the International Bureau of Weights and Measures (BIPM)?