BenchReference / Drill sizes / H H Drill Bit Decimal inches 0.2660″
Millimeters 6.756 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 6.8 mm 0.2677″ / 6.8 mm +0.044 mm (+0.0017″)
Fractional inch 17/64″ 0.2656″ / 6.747 mm −0.01 mm (−0.0004″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.965 mm (−0.0380″)
−0.541 mm +0.541 mm H F −0.229 mm G −0.127 mm I +0.152 mm J +0.279 mm 17/64″ −0.01 mm 6.8 mm +0.044 mm ← #1 −0.965 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.54 mm
Positive difference = cuts a slightly larger hole than H. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs H F 0.2570 6.528 −0.229 mm G 0.2610 6.629 −0.127 mm H 0.2660 6.756 — I 0.2720 6.909 +0.152 mm J 0.2770 7.036 +0.279 mm
← G (smaller) I (larger) →
Compare H 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 0.2660″. See all data sources .