3/8 inch in decimal and mm
Decimal inches
0.375 in
Millimetres
9.525 mm
From the standard, the international inch, 25.4 mm exactly
The math
- A fraction is its top number divided by its bottom number: 3/8 in = 3 ÷ 8 = 0.375 in.
- An inch is exactly 25.4 mm, so 0.375 × 25.4 = 9.525 mm.
- In feet, divide by 12: 0.375 ÷ 12 = 0.03125 ft. In centimetres, divide the mm by 10: 0.9525 cm.
- The same size in finer steps: 3/8 = 6/16 = 12/32 = 24/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.
Drills, plywood and lumber at 3/8 in
- 3/8 in drill bit
- Plywood, Performance Category 3/8
- Baltic birch sold as 3/8 (9 mm)
- 3/8 in rough hardwood
| Drill | Size | Off by |
|---|---|---|
| 9.5 mm | 0.374 in | −0.025 mm |
| 9.6 mm | 0.378 in | +0.075 mm |
Every drill is on the drill bit size chart.
Bits of this size
Sizes either side
Every size is on the fraction to decimal chart; any other size goes in the fraction to decimal calculator.