BenchReference

#78 Drill Bit

Decimal inches 0.0160″
Millimeters 0.406 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 1 mm 0.0394″ / 1 mm +0.594 mm (+0.0234″)
Fractional inch 1/64″ 0.0156″ / 0.397 mm −0.01 mm (−0.0004″)
Letter A 0.2340″ / 5.944 mm +5.537 mm (+0.2180″)
−0.15 mm+0.15 mm#78#80−0.064 mm#79−0.038 mm#77+0.051 mm#76+0.102 mm1/64″−0.01 mm1 mm +0.594 mm →A +5.537 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.15 mm
Positive difference = cuts a slightly larger hole than #78. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #78
#80 0.0135 0.343 −0.064 mm
#79 0.0145 0.368 −0.038 mm
#78 0.0160 0.406 —
#77 0.0180 0.457 +0.051 mm
#76 0.0200 0.508 +0.102 mm
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 number size is 0.0160″. See all data sources.