What's a penny nail?
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Q. Not an urgent question, but why are nails sometimes called by the “penny” such as a 16 penny nail. Everyone seems to have a slightly different answer, so I am asking you.

A.  Back in the 15th Century in England, nails were sold by the amount of money it cost to purchase “long 100” nails. At that time, the small monetary unit was the penny, abbreviated by the letter “d” which had come from the Roman coinage word denarius. Note that 240 pennies equaled 1 pound sterling. Also, due to a Germanic influence and some effort to work with base 12 instead of base 10, the quantity of “long 100” actually meant 120. (A lot of recent info about pennyweight for nails misses this point.)

So, a 16 penny (16 d.) nail is one that cost 16 pennies for 120 nails.

Today we have converted pennies into the length, so all 16 d. nails are 3-1/2 inches long. The length increases ¼ inch for each increase of 1 d up to 10 d. Then each increase in 2 d. is ¼ inch. At 20 d. each 10 d. increases the length by ½ inch. There is no specification about diameter.

2 d. = 1” long

4 d. = 1-1/2”

10 d. = 3”

12 d. = 3-1/4

16 d. = 3-1/2”

20 d. = 4”

Wow!  Confusing indeed without a good memory. So, today, most nails are sold by length and diameter and no reference is made to penny. There is no specification about diameter.

Hope this is enough info to keep you satisfied for now.

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About the author
Gene Wengert

Gene Wengert (1942-2025) was popularly known as “The Wood Doctor.” He trained thousands of people in efficient use of wood for more than 50 years and authored foundational resources on wood technology. He worked at the University of Wisconsin-Madison and Virginia Tech. His popular "Wood Doctor's Rx" column has appeared regularly in FDM and FDMC magazine since 1978. Because so much of his advice was timeless, he asked that we continue to run his columns in memoriam.