Penny (unit)

In the United States, the length of a nail is designated by its penny size, written with a number and the abbreviation d for penny; for example, 10d for a ten-penny nail. A larger number indicates a longer nail, shown in the table below. Diameter of the nail also varies based on penny size, depending on nail type. Nails under 1+1⁄4 inch, often called brads, are sold mostly in small packages with only a length designation or with length and wire gauge designations; for example, 1″ 18 ga. or 3⁄4″ 16 ga.

Penny sizes originally referred to the price for a hundred (100) or long hundred (120) nails in England in the 15th century:^[1] the larger the nail, the higher the cost per long hundred.^[2][3][4][5] The system remained in use in England into the 20th century,^{[citation needed]} but is obsolete there today. Nails are still designated in penny sizes in the United States.

In Canada, nails are specified by the type and length and are still manufactured to Imperial dimensions. Nail diameter is specified by gauge number (British Imperial Standard). The gauge is the same as the wire diameter used in the manufacture of the nail.^[6]

The d is an abbreviation for denarius, a Roman coin similar to a penny; this was the abbreviation for the monetary penny in the United Kingdom before decimalisation.

Penny size	Length (inches)	Length (nearest mm)
2d	1	25
3d	1+1⁄4	32
4d	1+1⁄2	38
5d	1+3⁄4	44
6d	2	51
7d	2+1⁄4	57
8d	2+1⁄2	64
9d	2+3⁄4	70
10d	3	76
12d	3+1⁄4	83
16d	3+1⁄2	89
20d	4	102
30d	4+1⁄2	114
40d	5	127
50d	5+1⁄2	140
60d	6	152

References

1. D. Nutt (1890). Archaeological Review: Volume 4. p. 322. In this connexion it is interesting to reflect that the proverbial "tenpenny nail" was a nail sold at 10d. for the long hundred.
2. "Penny" (subscription required). Oxford English Dictionary (2nd ed.). Retrieved May 30, 2010. Applied to nails, such adjectives denote the original price (in 15th c.) per hundred; as fivepenny nail, a nail which cost 5d. a hundred, tenpenny nail, a nail costing 10d. a hundred. (These names persisted after the prices fell, as they began to do in some places before 1500, and they were eventually used to designate sizes of nails.)^{[permanent dead link‍]}
3. Littlehales, H., ed. (1905). Medieval Records of a London City Church: Churchwardens Accounts and Memoranda (St. Mary at Hill) A.D. 1420–1559. Cited in the Oxford English Dictionary under "Penny" with a quote from 1426–1427.^{[page needed]}
4. "Penny". sizes.com. Retrieved January 10, 2010.
5. Norman Scott Brien Gras (1918). The Early English Customs System. Harvard University Press, Cambridge (Massachusetts). p. 701. Cited at sizes.com with a quote from 1507.
6. "Nails". The Canadian Wood Council – CWC.