BenchReference

#20 Drill Bit

Decimal inches 0.1610″
Millimeters 4.089 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 4.1 mm 0.1614″ / 4.1 mm +0.011 mm (+0.0004″)
Fractional inch 5/32″ 0.1563″ / 3.969 mm −0.121 mm (−0.0047″)
Letter A 0.2340″ / 5.944 mm +1.854 mm (+0.0730″)
−0.327 mm+0.327 mm#20#22−0.102 mm#21−0.051 mm#19+0.127 mm#18+0.216 mm5/32″−0.121 mm4.1 mm+0.011 mmA +1.854 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.33 mm
Positive difference = cuts a slightly larger hole than #20. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #20
#22 0.1570 3.988 −0.102 mm
#21 0.1590 4.039 −0.051 mm
#20 0.1610 4.089 —
#19 0.1660 4.216 +0.127 mm
#18 0.1695 4.305 +0.216 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 0.1610″. See all data sources.