BenchReference / Drill sizes / G G Drill Bit Decimal inches 0.2610″
Millimeters 6.629 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 6.6 mm 0.2598″ / 6.6 mm −0.029 mm (−0.0012″)
Fractional inch 17/64″ 0.2656″ / 6.747 mm +0.117 mm (+0.0046″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.838 mm (−0.0330″)
−0.53 mm +0.53 mm G E −0.279 mm F −0.102 mm H +0.127 mm I +0.279 mm 6.6 mm −0.029 mm 17/64″ +0.117 mm ← #1 −0.838 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.53 mm
Positive difference = cuts a slightly larger hole than G. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs G E 0.2500 6.35 −0.279 mm F 0.2570 6.528 −0.102 mm G 0.2610 6.629 — H 0.2660 6.756 +0.127 mm I 0.2720 6.909 +0.279 mm
← F (smaller) H (larger) →
Compare G 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 0.2610″. See all data sources .