1/8 Inch to MM
Fractional inch to millimeters
1/8 inch (1/8β³)
3.175 mm
= 0.3175 cm Β· 1 inch = 25.4 mm exactly
π‘ Commonly used for small tubing, bolts.
Nearby fractional inches
| Fraction | mm | cm |
|---|---|---|
| 1/16β³ | 1.5875 mm | 0.1588 cm |
| 1/8β³ | 3.175 mm | 0.3175 cm |
| 3/16β³ | 4.7625 mm | 0.4762 cm |
| 1/4β³ | 6.35 mm | 0.635 cm |
Also written as
1/8 to mm Β· 1/8 in mm Β· 1/8" in mm Β· 1/8 inch in mm Β· 1/8 inches to millimeters Β· 1/8 en mm Β· 0.125 inch to mm
All of these mean the same measurement. The double-prime mark (β³) and the plain quote (") both stand for inches, and en mm is simply the French and Spanish wording of the same question.
Closest metric drill size
3 mm
1/8β³ = 3.175 mm Β· difference 0.175 mm
Metric drills step in 0.5 mm, so a fractional inch size rarely lands exactly on one. A 0.175 mm gap is usually invisible in a clearance hole but changes the fit on a press fit or a tapped hole.
FAQ
How many mm is 1/8 inch?
1/8 inch equals 3.175 mm. Since one inch is defined as exactly 25.4 mm, the result is 25.4 Γ 1 Γ· 8.
Why is the value exact?
The international yard and pound agreement of 1959 fixed the inch at exactly 25.4 mm, so fractional inch conversions terminate rather than repeat.
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