Nail size converter
Convert US nail sizes from penny (8d, 16d…) to length in inches and millimeters, or a length to its penny size.
That's about the same as a framing nail (16d).
What it means
How long is that nail?
Lengths for common nails; the gauge (thickness) varies by type: common, box, sinker and finish nails of the same penny size differ in diameter.
Every unit
That nail in every unit
Learn
Three things worth knowing
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Divide by 4, add ½
Up to 10d: length in inches = penny ÷ 4 + ½. 8d is 2½ in.
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Pence per hundred
In 15th-century England the size was the price of a hundred nails in pennies; the d is the Roman denarius, the old abbreviation for a penny.
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16d box or common
A 16d box nail is as long as a 16d common nail but thinner; for structural framing the code may require common nails.
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Popular nail conversions
Background
About penny sizes
US nails are sold by the penny, written d. A 2d nail is 1 inch long and each penny adds ¼ inch up to 10d (3 in); after that the steps grow: 16d is 3½ in, the standard framing nail, and 60d is 6 in.