BenchReference / Drill sizes / A A Drill Bit Decimal inches 0.2340″
Millimeters 5.944 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 5.9 mm 0.2323″ / 5.9 mm −0.044 mm (−0.0017″)
Fractional inch 15/64″ 0.2344″ / 5.953 mm +0.01 mm (+0.0004″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −0.152 mm (−0.0060″)
−0.475 mm +0.475 mm A B +0.102 mm C +0.203 mm #1 −0.152 mm 5.9 mm −0.044 mm 15/64″ +0.01 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.48 mm
Positive difference = cuts a slightly larger hole than A. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs A A 0.2340 5.944 — B 0.2380 6.045 +0.102 mm C 0.2420 6.147 +0.203 mm
B (larger) →
Compare A 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 0.2340″. See all data sources .