Baker's dozen

A baker's dozen, long dozen, long measure, or Roughrider's dozen is 13

13 (number)

13 is the natural number after 12 and before 14. It is the smallest number with eight letters in its name spelled out in English. It is also the first of the teens – the numbers 13 through 19 – are the ages of teenagers....

, one more than a standard dozen

Dozen

Dozen is another word for the number twelve. The dozen may be one of the earliest primitive groupings, perhaps because there are approximately a dozen cycles of the moon or months in a cycle of the sun or year. The dozen is convenient because its multiples and divisors are convenient: 12 = 2 × 2 ×...

. The expression originated in 13^th century England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...

.

Origin

The oldest known source, but questionable explanation for the expression "baker's dozen" dates to the 13th century in one of the earliest English statute

Statute

A statute is a formal written enactment of a legislative authority that governs a state, city, or county. Typically, statutes command or prohibit something, or declare policy. The word is often used to distinguish law made by legislative bodies from case law and the regulations issued by...

s, instituted during the reign of Henry III

Henry III of England

Henry III was the son and successor of John as King of England, reigning for fifty-six years from 1216 to his death. His contemporaries knew him as Henry of Winchester. He was the first child king in England since the reign of Æthelred the Unready...

 (1216–1272), called the Assize of Bread and Ale

Assize of Bread and Ale

The Assize of Bread and Ale was a 13th-century statute in late medieval English law, which regulated the price, weight and quality of the bread and beer manufactured and sold in towns, villages and hamlets. This statute is usually attributed to act 51 Hen. III, occurring about 1266–1267. It was...

. Bakers who were found to have shortchanged customers could be subject to severe punishment. To guard against the punishment of losing a hand to an axe, a baker would give 13 for the price of 12, to be certain of not being known as a cheat. Specifically, the practice of baking 13 items for an intended dozen was insurance against "short measure", on the basis that one of the 13 could be lost, eaten, burnt, or ruined in some way, leaving the baker with the original legal dozen. The practice can be seen in the guild

Guild

A guild is an association of craftsmen in a particular trade. The earliest guilds were formed as confraternities of workers. They were organized in a manner something between a trade union, a cartel and a secret society...

 codes of the Worshipful Company of Bakers

Worshipful Company of Bakers

The Worshipful Company of Bakers is one of the Livery Companies of the City of London. The Bakers' Guild is known to have existed in the twelfth century. From the Corporation of London, the Guild received the power to enforce regulations for baking, known as the Assize of Bread and Ale. The...

 in London.

However, some doubt if this is the real explanation for the expression, because baking 13 instead of 12 units has been good practice all over Europe, not only in England. It also seems unusual that only bakers deliver 13 in a dozen, and not, for example, butchers. An alternative explanation for why specifically bakers deliver 13 in a dozen has been found in the tidy way 13 disks

Disk (mathematics)

In geometry, a disk is the region in a plane bounded by a circle.A disk is said to be closed or open according to whether or not it contains the circle that constitutes its boundary...

 (loaves, cookie

Cookie

In the United States and Canada, a cookie is a small, flat-baked treat, usually containing fat, flour, eggs and sugar. In most English-speaking countries outside North America, the most common word for this is biscuit; in many regions both terms are used, while in others the two words have...

s, biscuit

Biscuit

A biscuit is a baked edible product. The word applies to two distinctly different products in American and British English.*In American English it relates to a small soft leavened bread, somewhat similar to a scone...

s, etc.) can pack

Packing problem

Packing problems are a class of optimization problems in recreational mathematics which involve attempting to pack objects together , as densely as possible. Many of these problems can be related to real life storage and transportation issues...

 a rectangle

Rectangle

In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle. A rectangle with vertices ABCD would be denoted as ....

 (baking tray) of appropriate proportions. Packing trays have a 3:2 aspect ratio, and the most efficient two-dimensional array is hexagonal close packing, which has sixfold symmetry, such that each baked item is equidistant from its six nearest neighbors. The corners of a cookie sheet heat up and cool off faster than the edges and interior, so any item placed near a corner will not bake at the same rate as the other items. A 4+5+4 arrangement provides the dense hexagonal packing while avoiding corners, and would have been discovered empirically by bakers with the goal of baking the maximum number per batch with optimal uniformity.
According to the 1811 Dictionary of the Vulgar Tongue, by Capatin Grose, a Baker's Dozen is "Fourteen; that number of rolls being allowed to the purchaser of a dozen".