BenchReference / Drill sizes / C C Drill Bit Decimal inches 0.2420″
Millimeters 6.147 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 6.1 mm 0.2402″ / 6.1 mm −0.047 mm (−0.0018″)
Fractional inch 15/64″ 0.2344″ / 5.953 mm −0.194 mm (−0.0076″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.356 mm (−0.0140″)
−0.492 mm +0.492 mm C A −0.203 mm B −0.102 mm D +0.102 mm E +0.203 mm #1 −0.356 mm 15/64″ −0.194 mm 6.1 mm −0.047 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.49 mm
Positive difference = cuts a slightly larger hole than C. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs C A 0.2340 5.944 −0.203 mm B 0.2380 6.045 −0.102 mm C 0.2420 6.147 — D 0.2460 6.248 +0.102 mm E 0.2500 6.35 +0.203 mm
← B (smaller) D (larger) →
Compare C 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 letter size is 0.2420″. See all data sources .