BenchReference / Drill sizes / 12.7 mm 12.7 mm Drill Decimal inches 0.5000″
Millimeters 12.7 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 1/2″ 0.5000″ / 12.7 mm exact Number (wire gauge) #1 0.2280″ / 5.791 mm −6.909 mm (−0.2720″)
Letter Z 0.4130″ / 10.49 mm −2.21 mm (−0.0870″)
−1.016 mm +1.016 mm 12.7 mm = 1/2″ 12.5 mm −0.2 mm 12.6 mm −0.1 mm 12.8 mm +0.1 mm 12.9 mm +0.2 mm ← #1 −6.909 mm ← Z −2.21 mm tick position = true diameter · metric neighbors above, equivalents below · window ±1.02 mm
Positive difference = cuts a slightly larger hole than 12.7 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring metric sizes Drill Decimal in mm vs 12.7 mm 12.5 mm 0.4921 12.5 −0.2 mm 12.6 mm 0.4961 12.6 −0.1 mm 12.7 mm 0.5000 12.7 — 12.8 mm 0.5039 12.8 +0.1 mm 12.9 mm 0.5079 12.9 +0.2 mm
← 12.6 mm (smaller) 12.8 mm (larger) →
Compare 12.7 mm 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 metric size is 12.7 mm. See all data sources .