Nail Size Chart
Nail sizes are measured using the penny system, abbreviated with the letter "d" (from the Roman word "denarius"). A higher penny number means a longer, thicker nail. The chart below lists all standard penny sizes from 2d through 60d with their exact length and diameter measurements in both imperial and metric units.
| Penny Size | Length (in) | Length (mm) | Gauge | Diameter (in) | Common Use |
|---|---|---|---|---|---|
| 2d | 1.00" | 25.4 mm | 15 | 0.072" | Small trim, crafts |
| 3d | 1.25" | 31.8 mm | 14 | 0.080" | Finish trim, light molding |
| 4d | 1.50" | 38.1 mm | 12 | 0.098" | Small trim, casing, baseboards |
| 6d | 2.00" | 50.8 mm | 11 | 0.113" | Finish carpentry, siding, sheathing |
| 8d | 2.50" | 63.5 mm | 10 | 0.131" | General framing, sheathing, subflooring |
| 10d | 3.00" | 76.2 mm | 9 | 0.148" | Framing, structural connections |
| 12d | 3.25" | 82.6 mm | 9 | 0.148" | Framing, boxing, crating |
| 16d | 3.50" | 88.9 mm | 8 | 0.162" | Most common framing nail, wall studs |
| 20d | 4.00" | 101.6 mm | 6 | 0.192" | Heavy framing, headers, beams |
| 30d | 4.50" | 114.3 mm | 5 | 0.207" | Heavy construction, timber framing |
| 40d | 5.00" | 127.0 mm | 4 | 0.225" | Heavy structural, post and beam |
| 60d | 6.00" | 152.4 mm | 2 | 0.263" | Extra-heavy construction, timber connections |
The Penny Size System
Origin of the Penny System
The penny system dates back to 15th-century England, where it originally referred to the price of 100 nails. A "10 penny" nail cost 10 pennies per hundred. Over time, the price changed but the sizing convention stuck. Today, the "d" abbreviation comes from "denarius," the Roman coin equivalent to a penny.
Most Common Framing Nail
The 16d (sixteen penny) nail at 3.5 inches long is the most widely used framing nail. Building codes specify 16d nails for connecting wall studs to plates, joists to headers, and rafters to ridge boards. A typical 2x4 stud wall uses 16d nails throughout. For toenailing, 8d nails are standard.
Wire Gauge and Diameter
Nail gauge follows the American Wire Gauge (AWG) system, where lower numbers mean thicker nails. A 16d nail is 8 gauge (0.162 inches diameter), while a 2d finish nail is 15 gauge (0.072 inches diameter). Thicker nails provide more shear strength but are more likely to split thin or dry wood.