BenchReference / Drill sizes / D D Drill Bit Decimal inches 0.2460″
Millimeters 6.248 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 6.2 mm 0.2441″ / 6.2 mm −0.048 mm (−0.0019″)
Fractional inch 1/4″ 0.2500″ / 6.35 mm +0.102 mm (+0.0040″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.457 mm (−0.0180″)
−0.5 mm +0.5 mm D B −0.203 mm C −0.102 mm E +0.102 mm F +0.279 mm #1 −0.457 mm 6.2 mm −0.048 mm 1/4″ +0.102 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.5 mm
Positive difference = cuts a slightly larger hole than D. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs D B 0.2380 6.045 −0.203 mm C 0.2420 6.147 −0.102 mm D 0.2460 6.248 — E 0.2500 6.35 +0.102 mm F 0.2570 6.528 +0.279 mm
← C (smaller) E (larger) →
Compare D 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 0.2460″. See all data sources .