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tum [Swedish]

In Sweden, a small unit of length, literally “thumb”. Officially from 1665 to 1863, and permitted to 1878, the tum was legally defined as 1/12th of a fot, about 2.474 centimeters (about 0.97 inches).

In the 1730's Sweden developed a new system of length measures based on dividing the fot decimally. In this system, in official use from 1739 to 1878, and permissible up to the introduction of the metric system in 1889, the tum = 1/10 of a fot, about 29.690 cm.

Between 1739 and 1878 the two tums were legally in simultaneous use: the older (often called a verktum) for building, handicrafts and commerce, while the decimaltum was used for “geometrical” mensuration. Sources in the 19th century say the decimal tum was by then used for all purposes. This seems, however, not to have been the case.

In the 20ᵗʰ century, the Swedish government reported to the United Nations (UN, 1966) that the tum was still in use at a value of 2.474 centimeters, which is the verktum. The older unit has survived and the newer perished. In the early 21st century, the tum was being used to describe the size of television screens, and bicycle frames and wheels.