# DIY Dictionary: 16d Nail

Updated: Mar. 03, 2022

What is a 16d Nail? A 16d nail is one that is 3-1/2 inches long. But what does the ‘d’ stand for? There are a few possible explanations…

## What is a 16d Nail?

A 16d nail is one that’s 3-1/2-inches long. But what the heck does the “d” stand for? After all, it’s used to describe the length of finish, box, common and other nails. One explanation is that the “d” hearkens back to the era when Romans ruled England and the monetary unit was the denarius (which had the same value as an English penny.) Legend has it that one hundred 3-1/2-inch nails cost 16 pennies back then. And it would follow suit that one hundred 2-inch (or 6d) nails cost, well, 6 pennies. So, it’s an archaic term, but is apparently one that’s here to stay.

For trivia lovers, there is a formula for translating “d” or penny length into real lengthâ€”sort of. Divide the “d” number by four, then add 1/2 inch to arrive at the actual nail length. To determine the length of a 4d nail, divide by four (that gives you 1) then add the 1/2 inch. Bingo, your 4d nail is 1-1/2-inches long. This formula works for nails up to 10d in lengthâ€”after that it no longer works and you’re on your own.