BenchReference / Drill sizes / 1/8″ 1/8″ Drill Bit Decimal inches 0.1250″
Millimeters 3.175 mm
System Fractional inch
In 64ths 8/64″
Nearest equivalents in other systems System Nearest drill Size Difference Metric 3.2 mm 0.1260″ / 3.2 mm +0.025 mm (+0.0010″)
Number (wire gauge) #30 0.1285″ / 3.264 mm +0.089 mm (+0.0035″)
Letter A 0.2340″ / 5.944 mm +2.769 mm (+0.1090″)
−0.254 mm +0.254 mm 1/8″ 3.2 mm +0.025 mm #30 +0.089 mm ← 3/32″ −0.794 mm ← 7/64″ −0.397 mm 9/64″ +0.397 mm → 5/32″ +0.794 mm → tick position = true diameter · fractional neighbors above, equivalents below · window ±0.25 mm
Positive difference = cuts a slightly larger hole than 1/8″. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring fractional sizes Drill Decimal in mm vs 1/8″ 3/32″ 0.0938 2.381 −0.794 mm 7/64″ 0.1094 2.778 −0.397 mm 1/8″ 0.1250 3.175 — 9/64″ 0.1406 3.572 +0.397 mm 5/32″ 0.1563 3.969 +0.794 mm
← 7/64″ (smaller) 9/64″ (larger) →
Compare 1/8″ with another size
Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this fractional size is 0.1250″. See all data sources .