Fractional inches to millimetres
Handy for drill bits, sockets, spanners and plumbing fittings sold in imperial sizes.
| Inches | Millimetres | Inches | Millimetres |
|---|---|---|---|
| 1/16" | 1.59 mm | 9/16" | 14.29 mm |
| 1/8" | 3.17 mm | 5/8" | 15.88 mm |
| 3/16" | 4.76 mm | 11/16" | 17.46 mm |
| 1/4" | 6.35 mm | 3/4" | 19.05 mm |
| 5/16" | 7.94 mm | 13/16" | 20.64 mm |
| 3/8" | 9.52 mm | 7/8" | 22.22 mm |
| 7/16" | 11.11 mm | 15/16" | 23.81 mm |
| 1/2" | 12.70 mm | 1" | 25.40 mm |
Inches to centimetres (1–12 inches)
| Inches | cm | mm |
|---|---|---|
| 1" | 2.54 cm | 25.4 mm |
| 2" | 5.08 cm | 50.8 mm |
| 3" | 7.62 cm | 76.2 mm |
| 4" | 10.16 cm | 101.6 mm |
| 5" | 12.70 cm | 127.0 mm |
| 6" | 15.24 cm | 152.4 mm |
| 7" | 17.78 cm | 177.8 mm |
| 8" | 20.32 cm | 203.2 mm |
| 9" | 22.86 cm | 228.6 mm |
| 10" | 25.40 cm | 254.0 mm |
| 11" | 27.94 cm | 279.4 mm |
| 12" | 30.48 cm | 304.8 mm |
Common building conversions
- Timber sizes: the old "4 × 2" is sold in Australia as 90 × 45 mm (dressed), and "3 × 2" as 70 × 35 mm.
- Plasterboard sheets: 2400 × 1200 mm is close to the imperial 8 × 4 ft (2438 × 1219 mm), but not identical.
- House size: 1 "square" = 100 ft² = 9.29 m².
- Pipe sizes: nominal pipe sizes aren't exact measurements. A "½ inch" pipe fitting is DN15 in metric plumbing.
Questions
How many centimetres in an inch?
One inch is exactly 2.54 cm (25.4 mm). To convert inches to cm, multiply by 2.54. To convert cm to inches, divide by 2.54.
How do I convert mm to inches?
Divide millimetres by 25.4. For example, 100 mm ÷ 25.4 = 3.94 inches.
How many square feet in a square metre?
One square metre is about 10.764 square feet. One square foot is 0.0929 m².
What is a "square" in Australian house sizes?
An old imperial building measure still used in real estate: one square is 100 square feet, or about 9.29 m². A 25-square house is about 232 m².
What is 3/8 of an inch in mm?
3/8" is 9.525 mm, usually rounded to 9.5 mm. The table on this page lists every fraction from 1/16" to 1".
Estimates only. Check the product label and your measurements before you buy. More free tools: see them all.