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The Letter 'd' in Nail Sizes

Carpenters always talk about 16d common nails or 8d finish nails or 10d sinkers, but nobody ever explains what the heck ‘d’ means. This article does.

By the DIY experts of The Family Handyman Magazine

Understanding “d” sizes

The “d” stands for penny, so 8d refers to an 8-penny nail, 16d to a 16-penny nail and so on. It’s a way to indicate nail length, as you can see in the table below.

Now for the obvious question: Where does the sizing system come from and why does “d” stand for penny? The “d” goes way back to the time when the Romans occupied what is now England. The “d” is associated with a Roman coin called the denarius, which was also the name for an English penny.

So what’s that got to do with nails? It was associated with nails when they were hand-forged, one at a time. Some say a hundred 3-1/2 inch nails would have cost 16 pennies and thus became known as 16-penny nails. Others say that the number and the “d” indicate that one 16d (3-1/2 inch) hand-forged nail cost 16 pennies.

Who knows which version is true, or why the “d” designation persists even in the building codes today, but fortunately, retail boxes of nails are marked with the penny size as well as the length in inches. As you can see in the photo, length is only one factor of many in choosing a nail.

Conversion chart

Conversion chart

Size Conversion Chart

Print out this handy reference chart and tape it in your tool box, just in case you forget.

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August 15, 5:26 PM [GMT -5]

in Britain nails were traditionally sold by weight ie. 1lb of 1-1/2" nails cost 4d or four pennies, and so on.bryon1

March 07, 9:13 PM [GMT -5]

Interesting... but you could point out the reasons for choosing box over common nails... standard head nail vs. duplex...casing vs. finish nails...also, what's a "sinker" nail vs regular nail and why use one.
Also, what's the conversion w/ nail gun sizes... most nail gun nails are very skinny vs even box nails.
I like the article, but it needs more details.

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The Letter 'd' in Nail Sizes

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