1/8 inch to decimal and mm
1/8" = 0.125" = 3.175 mm
An eighth of an inch shows up everywhere: plywood reveals, shim stock, small drill bits and the spacing between tiles. It's an easy one to remember because it ends in a clean 125.
To get the decimal, divide the top number by the bottom: 1 ÷ 8 = 0.125. For millimeters, multiply that by 25.4, which gives 3.175 mm (about 3.2 mm if you're working with a metric ruler).
Nearby sizes in 64ths
| Fraction | Decimal (in) | Millimeters |
|---|---|---|
| 1/16" | 0.062500 | 1.587 mm |
| 5/64" | 0.078125 | 1.984 mm |
| 3/32" | 0.093750 | 2.381 mm |
| 7/64" | 0.109375 | 2.778 mm |
| 1/8" | 0.125000 | 3.175 mm |
| 9/64" | 0.140625 | 3.572 mm |
| 5/32" | 0.156250 | 3.969 mm |
| 11/64" | 0.171875 | 4.366 mm |
| 3/16" | 0.187500 | 4.762 mm |
Need a different value or want to round to 1/32 or 1/64? Use the full converter.