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[2][3][4][5] The system remained in use in England into the 20th century,[citation needed] but is obsolete there today.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).