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Size Of Nails

In most of the world, nails are described by their dimensions in millimeters, for example “150 × 4” is a nail 150 mm long and 4 mm in diameter. A description of the head and finish is typically added. In the United States, however, some types of nails are sized in pennies(symbol, d), a system that originated in England centuries ago.

For the problem of substituting nails sized in newer formats for nails sized in pennies, seenails spec'ed in pennys in the age of nail guns



In the United States, the lengths and diameters of some types of nails are indicated by their size in pennies. An 8d finishing nail and an 8d common nail are about the same length, but have different diameters.


As rules of thumb,

  • In fastening sheathing, shingles, clapboard, etc.,      the nail should be at least three times longer than the thickness of the      sheet or board being fastened with it.

  • A nail driven perpendicular to the grain should      penetrate the lumber a minimum of 12 times its diameter. Building codes      often call for at least half the length of the nail.

Longer is not necessarily better; the longer the nail, the greater the danger of splitting the wood.