1/4 inch to decimal and mm
1/4" = 0.25" = 6.350 mm
A quarter inch is probably the most used fraction in the shop: 1/4-20 bolts, 1/4" plywood, router bits and hex drivers all use it.
To get the decimal, divide the top number by the bottom: 1 ÷ 4 = 0.25. For millimeters, multiply that by 25.4, which gives 6.350 mm (about 6.3 mm if you're working with a metric ruler).
Nearby sizes in 64ths
| Fraction | Decimal (in) | Millimeters |
|---|---|---|
| 3/16" | 0.187500 | 4.762 mm |
| 13/64" | 0.203125 | 5.159 mm |
| 7/32" | 0.218750 | 5.556 mm |
| 15/64" | 0.234375 | 5.953 mm |
| 1/4" | 0.250000 | 6.350 mm |
| 17/64" | 0.265625 | 6.747 mm |
| 9/32" | 0.281250 | 7.144 mm |
| 19/64" | 0.296875 | 7.541 mm |
| 5/16" | 0.312500 | 7.938 mm |
Need a different value or want to round to 1/32 or 1/64? Use the full converter.