QUDT includes information that can be used to convert measurements from one unit to another. This is a workhorse for merging quantitative information on the Semantic Web. Conversions can be within the same system of units (meters to kilometers, seconds to hours, feet to miles) or crossing between systems (miles to kilometers, degrees Fahrenheit to degrees Centigrade). In order for such a conversion to make sense, the units must be commensurate—that is, they measure the same kind of thing. Miles and kilometers are both measurements of length, so it makes sense to consider a conversion between the two. Seconds and degrees Fahrenheit do not measure the same thing; it is not meaningful to convert from one to another.