1/2 inch in decimal and mm
Decimal inches
0.5 in
Millimetres
12.7 mm
From the standard, the international inch, 25.4 mm exactly
The math
- A fraction is its top number divided by its bottom number: 1/2 in = 1 ÷ 2 = 0.5 in.
- An inch is exactly 25.4 mm, so 0.5 × 25.4 = 12.7 mm, or 12.700 mm to three places.
- In feet, divide by 12: 0.5 ÷ 12 = 0.041667 ft. In centimetres, divide the mm by 10: 1.27 cm.
- The same size in finer steps: 1/2 = 4/8 = 8/16 = 16/32 = 32/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.
Drills, plywood and lumber at 1/2 in
- 1/2 in drill bit
- Plywood, Performance Category 1/2
- Baltic birch sold as 1/2 (12 mm)
- 1/2 in rough hardwood
| Drill | Size | Off by |
|---|---|---|
| 12.6 mm | 0.4961 in | −0.1 mm |
| 12.8 mm | 0.5039 in | +0.1 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.