BenchReference / Drill sizes / 1/2″ 1/2″ Drill Bit Decimal inches 0.5000″
Millimeters 12.7 mm
System Fractional inch
In 64ths 32/64″
Nearest equivalents in other systems System Nearest drill Size Difference Metric 12.7 mm 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 1/2″ = 12.7 mm 15/32″ −0.794 mm 31/64″ −0.397 mm 33/64″ +0.397 mm 17/32″ +0.794 mm ← #1 −6.909 mm ← Z −2.21 mm tick position = true diameter · fractional neighbors above, equivalents below · window ±1.02 mm
Positive difference = cuts a slightly larger hole than 1/2″. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring fractional sizes Drill Decimal in mm vs 1/2″ 15/32″ 0.4688 11.906 −0.794 mm 31/64″ 0.4844 12.303 −0.397 mm 1/2″ 0.5000 12.7 — 33/64″ 0.5156 13.097 +0.397 mm 17/32″ 0.5313 13.494 +0.794 mm
← 31/64″ (smaller) 33/64″ (larger) →
Compare 1/2″ 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 0.5000″. See all data sources .