Sources and scope for this page: ASTM F1667-22, covering the common nail dimensions, penny sizes and shank diameters; and ASME B18.27 — Tapered and Reduced Section Headed Fasteners (withdrawn; the nail standard is now ASTM F1667), covering historical nail dimension definitions (one more source is tabulated below). No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. Full sources, values and limits on this page.
Page last changed 2026-10-19 · based on ASTM F1667-22
Quick Answer
Common Wire Nail Sizes
| Penny size[1] | Length in[1] | Shank diameter in[1] | Length mm[2] | Shank diameter mm[2] | Typical use[1] |
|---|---|---|---|---|---|
| 2d # | 1.00 | 0.0720 | 25.4 | 1.83 | Small trim and moulding |
| 3d # | 1.25 | 0.0800 | 31.8 | 2.03 | Light trim, cabinet backs |
| 4d # | 1.50 | 0.0990 | 38.1 | 2.51 | Trim, small casing |
| 5d # | 1.75 | 0.1010 | 44.4 | 2.57 | Casing and baseboard |
| 6d # | 2.00 | 0.1130 | 50.8 | 2.87 | General framing for light members, fencing |
| 7d # | 2.25 | 0.1130 | 57.1 | 2.87 | Interior trim, sheathing |
| 8d # | 2.50 | 0.1310 | 63.5 | 3.33 | The general-purpose framing nail — studs, sheathing, decking |
| 9d # | 2.75 | 0.1310 | 69.8 | 3.33 | Interior framing |
| 10d # | 3.00 | 0.1480 | 76.2 | 3.76 | Framing, subflooring |
| 12d # | 3.25 | 0.1480 | 82.5 | 3.76 | Framing and decking |
| 16d # | 3.50 | 0.1620 | 88.9 | 4.11 | The heavy framing nail — joists, rafters, headers |
| 20d # | 4.00 | 0.1920 | 101.6 | 4.88 | Heavy framing, deck framing |
| 30d # | 4.50 | 0.2070 | 114.3 | 5.26 | Timber and pole construction |
| 40d # | 5.00 | 0.2250 | 127.0 | 5.71 | Heavy timber, marine construction |
| 50d # | 5.50 | 0.2440 | 139.7 | 6.20 | Heavy timber and cribbing |
| 60d # | 6.00 | 0.2620 | 152.4 | 6.65 | Heavy timber and cribbing |
Dimensions are for common wire nails, the general-purpose round nail. Other nail types share the penny-size names but not the dimensions: box nails are thinner than common nails at the same penny size (a 16d box is 0.148 in against the common 0.162), and finishing, casing, roofing and duplex nails each have their own shank sizes. Always confirm which type a specification means — "16d nail" is ambiguous and the difference in shank diameter is about 10%.
What a Penny Size Actually Means
The "d" in 8d stands for denarius, a Roman silver coin. The penny size was originally the price of one hundred nails of that size in medieval England — a hundred 2d nails cost twopence. The sizes were standardised and the prices were not, so the system survived as a naming convention with no arithmetic content at all.
That is why there is no formula. The penny number is a label, and the relationship between the number and the dimensions is historical. Some regularities exist — from 2d to 10d each 2 penny steps adds 1/2 in of length — but the pattern breaks at 12d and changes again at 16d, and the diameter does not follow the same steps as the length at all. Anyone who tries to compute a nail length from its penny size will be wrong.
The practical consequence is that penny sizes must be looked up. The two that matter most in framing are 8d and 16d: 8d for sheathing, studs and general work, and 16d for joists, rafters and headers. A framing specification is often written entirely in those two sizes.
Nail Length, Diameter and Holding Power
Holding power in wood comes mostly from the shank diameter and the length of shank in the lower member, not from the length overall. A nail's withdrawal resistance is roughly proportional to the diameter raised to a power and to the depth of penetration into the piece being held.
The traditional rule for framing is that the nail should penetrate the member being held by at least half its length, and that a nail driven into end grain — as when nailing a stud to a plate — holds only about two-thirds as well as one driven across the grain. That is why framing practice uses two nails per joint rather than one longer nail: the second nail adds more capacity than extra length on the first.
Diameter matters more than most people expect. Going from an 8d (0.131 in) to a 16d (0.162 in) is a 24% increase in diameter and roughly a 50% increase in cross-section, which translates into a large gain in both holding power and shear strength. That is the real reason a framer reaches for the bigger nail on a structural joint, not the extra inch of length.
Note also that nails are sized by shank diameter before galvanising. A hot-dip galvanised nail is thicker than its nominal figure by the coating thickness, which can be enough to split a thin piece of hardwood that the bare nail would have entered cleanly.
Frequently Asked Questions
- What does the d mean in 16d nails?
- It stands for denarius, a Roman coin. The penny size was originally the price per hundred nails in medieval England, so a 16d nail cost sixteen pence per hundred. Prices changed and the nail sizes were standardised, so the designation survived as a name with no arithmetic meaning — there is no formula relating the penny number to the length or diameter.
- How long is an 8d nail?
- 2.5 in, or 63.5 mm, with a 0.131 in (3.3 mm) shank diameter in the common nail series. It is the general-purpose framing nail for studs, sheathing and decking. A 16d is 3.5 in (89 mm) with a 0.162 in shank and is the heavy framing nail for joists and rafters.
- Is a box nail the same as a common nail?
- No — a box nail has a smaller shank diameter than a common nail at the same penny size. A 16d common nail is 0.162 in; a 16d box nail is about 0.148 in, roughly 9% thinner. Box nails are less likely to split thin or dry lumber, but they also hold less. A specification that says "16d nail" without naming the type is ambiguous, and the difference matters in structural work.
- How much of the nail should penetrate?
- Framing practice is that the nail should penetrate the member being held by at least half its length. The reason is that the nail's grip comes from the shank in the lower member — the part passing through the upper member contributes almost nothing. Driving into end grain reduces holding power further, to roughly two-thirds of the cross-grain value, which is why joints in end grain get extra nails.
- Do galvanised nails have different dimensions?
- Electroplated galvanised nails are within a few thousandths of an inch of the bare size. Hot-dip galvanised nails have a much thicker coating — typically 0.0015 to 0.0025 in per surface — so the installed diameter is noticeably larger. That can be enough to split hardwood or thin stock that the bare nail would have entered cleanly, and it is why hot-dip nails are specified by their coating class as well as their size.
Related
Value Sources
References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.
| # | Source | Type | Revision / method |
|---|---|---|---|
| [1] | ASTM F1667 — Driven Fasteners: Nails, Spikes and Staples | reference | ASTM F1667-22 |
| [2] | Value computed from the standard's defining relationship | derived | Computed at build time from the defining formula stated on the page and verified against every row, then checked against known standard values held as anchors. Nothing in this column was transcribed. |
Data Sources
| Standard | Revision | What it covers on this page |
|---|---|---|
| ASTM F1667 — Driven Fasteners: Nails, Spikes and Staples | ASTM F1667-22 | the common nail dimensions, penny sizes and shank diameters |
| ASME B18.27 — Tapered and Reduced Section Headed Fasteners | n/a — withdrawn; the nail standard is now ASTM F1667 | historical nail dimension definitions |
| NIST Handbook 44 — Specifications, Tolerances and Other Technical Requirements | NIST Handbook 44, 2024 edition | the retail sale requirements for nails sold by size |
Verification scope
No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.
Derived values — the following values on this page are calculated, not taken directly from the standard:
| Value | How it is derived |
|---|---|
| Length and shank diameter in millimetres | Inch dimension × 25.4, recomputed at build time for every row. 2.50 in is held as a known-value check at 63.5 mm. |
Dimensions are for common wire nails. Box, casing, finishing, roofing, duplex and screw-shank nails share penny-size names but have different shank diameters — a 16d box nail is about 9% thinner than a 16d common nail. Shank diameters are before coating; hot-dip galvanised nails are noticeably thicker in service. Confirm the nail type, not just the penny size, before specifying.
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