The first description of a shoe sizing system was made and recorded by British genealogist, Randle Holme III (1627–1700) in the Academy of Armory and Blazon in 1688. Three barley corns came to represent an inch and had been used since the 10th-century when it appeared in Welsh Laws of Hywel Dda. Around 1300, it became incorporated into The Yards and Perches statutes and continued to be in force until the 1824 Weights and Measures Act. Although it was claimed the average length of a grain of barley was 0.345 in (8.8 mm), the actual length of a kernel of barley varied from as short as 4–7 mm (0.16–0.28 in) to as long as 12–15 mm (0.47–0.59 in). Whilst the barleycorn was frequently taken as a measure of length equal to 1/4 inch, shoemakers used them as equal to 1⁄3" , (approx 0.8467 cm) to measure their lasts. The absence of an enforced standard has resulted in a variation in shoe measurements, ever since.
The UK System starts from the smallest size deemed practical, which is called size zero. This is the equivalent to four inches (101.6 mm, or 12 baley corns), and sizes go up to size 13 1⁄2 (21.59 cm , or 8 1⁄2" , or 25 1⁄2 barley corns). The UK Shoe Size System for children is divided into 13 parts. There is 8.4mm (1/4 ") between whole sizes, and 4.2mm between half sizes. Adults sizes range from size 1 (8 2⁄3 in, 26 barleycorns or 22.01 cm) to size 15 (equivalent to 12"). It is not formally standardised.
It is not clear why a unit of 13 was used to judge a critical point between child sizes and adults. The origins of this remain clouded but there are several theories. It is understood early English shoemakers started with the smallest size (0 or 1) at four inches because it was an easy measure to record i.e. the width across the knuckles and happened to correspond to the size of a child’s foot when they needed their first pair of shoes.
The next easy measure was the span of the hand or 9". The span of the hand plus the easure across the knuckles (4") gave 13". This measured the average length of a child's foot at puberty. Adult sizes would logically start at the end of the child's size.
Another possible reason given by some shoe historians is when shoe size sticks when were introduced they measured twelve inches, with the units measured from zero. This meant twelve became thirteen and shoemakers generally accepted 13 as the base unit for measuring feet.
There were several attempts to standardise shoe measurements and adopt the quarter inch unit however, arguments always failed due to costs and problems of changing to a new system. Holme, suggested the "guild of shoemakers" agree on a common size scale based on a quarter inch (rather than the third of inch) but little changed by the nineteenth century, when Gardener described in 1856 a shoe sizing system based on one-third inch, scale. The barleycorn, for all its metrological shortcomings, continues to be used in both American and English sizing systems.
Until the time of Queen Victoria, children's shoes were made as miniature adult shoes, with no special feature for growing feet. The children of the Middle Class in Victorian times wore shoe styles more akin to fancy dress which may account for why the design of today's shoes contain motifs which refer to previous ages and classic periods of history.
Going barefoot is still within living memory and many children went without footwear as a normal practice and not through poverty. Work shoes were often handed down with the better off wearing them before passing them to siblings.