The barleycorn is the smallest Anglo-Saxon unit of length. Notionally the length of a corn of barley, its actual length was determined in relation to a particular rod of metal, typically a yard-bar, and thus 1/108th of a yard, 1/36 of foot, or 1/3 of an inch. The unit was nominally the base unit from which the inch was defined. Three barleycorns comprising 1 inch was the legal definition of the inch in many medieval laws, both of England and Wales, from the 10th-century Laws of Hywel Dda to the 1324 definition of the inch enacted by Edward II. Note the relation to the grain.
This archaic measure is still the basis for current shoe sizes in Great Britain & Ireland, with each (whole-numbered) shoe size differing from the next by the length of one barleycorn. Unlike the UK, the US & Canada use inches for shoe size measurement.
- "Barley corn". Britannica. Edinburgh. 1769.
- Zupko, Ronald Edward (1977). British Weights and Measures: A History from Antiquity to the Seventeenth Century. University of Wisconsin Press. p. 21. ISBN 978-0-299-07340-4.