BenchReference / Drill sizes / 6.3 mm 6.3 mm Drill Decimal inches 0.2480″
Millimeters 6.3 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 1/4″ 0.2500″ / 6.35 mm +0.05 mm (+0.0020″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.509 mm (−0.0200″)
Letter E 0.2500″ / 6.35 mm +0.05 mm (+0.0020″)
−0.504 mm +0.504 mm 6.3 mm 6.1 mm −0.2 mm 6.2 mm −0.1 mm 6.4 mm +0.1 mm 6.5 mm +0.2 mm 1/4″ +0.05 mm E +0.05 mm ← #1 −0.509 mm tick position = true diameter · metric neighbors above, equivalents below · window ±0.5 mm
Positive difference = cuts a slightly larger hole than 6.3 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring metric sizes Drill Decimal in mm vs 6.3 mm 6.1 mm 0.2402 6.1 −0.2 mm 6.2 mm 0.2441 6.2 −0.1 mm 6.3 mm 0.2480 6.3 — 6.4 mm 0.2520 6.4 +0.1 mm 6.5 mm 0.2559 6.5 +0.2 mm
← 6.2 mm (smaller) 6.4 mm (larger) →
Compare 6.3 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 6.3 mm. See all data sources .