Inches to Millimeters
Conversion Table
| Inches | Millimeters |
|---|---|
| 1/16 in | 1.5875 mm |
| 1/8 in | 3.175 mm |
| 1/4 in | 6.35 mm |
| 3/8 in | 9.525 mm |
| 1/2 in | 12.7 mm |
| 5/8 in | 15.875 mm |
| 3/4 in | 19.05 mm |
| 7/8 in | 22.225 mm |
| 1 in | 25.4 mm |
| 1.5 in | 38.1 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127.0 mm |
| 6 in | 152.4 mm |
| 8 in | 203.2 mm |
| 10 in | 254.0 mm |
| 12 in | 304.8 mm |
| 18 in | 457.2 mm |
| 24 in | 609.6 mm |
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Facts
- The inch was originally defined as the width of a man's thumb.
- Screen sizes (phones, TVs, monitors) are measured in inches diagonally.
- Pipe sizes and bolt sizes in the US are measured in inches.
- One inch = 25.4 mm exactly, by international agreement.
Frequently Asked Questions
There are exactly 25.4 millimeters in one inch. This is an internationally standardized definition established in 1959. To convert inches to millimeters, multiply the inch value by 25.4.
1/4 inch equals 6.35 mm (0.25 × 25.4 = 6.35). This is a common size for screws, bolts, and drill bits used in woodworking and construction.
3/8 inch equals 9.525 mm (0.375 × 25.4 = 9.525). This is a standard socket drive size and a common measurement for plumbing fittings.
First convert the fraction to a decimal (e.g., 3/8 = 0.375), then multiply by 25.4. So 3/8 inch = 0.375 × 25.4 = 9.525 mm. Alternatively, multiply the numerator by 25.4 and divide by the denominator: (3 × 25.4) / 8 = 9.525 mm.
1/2 inch equals exactly 12.7 mm (0.5 × 25.4 = 12.7). This is one of the most commonly used fractional inch sizes in hardware, pipe fittings, and ratchet socket drives.