BenchReference

#8 Drill Bit

Decimal inches 0.1990″
Millimeters 5.055 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 5.1 mm 0.2008″ / 5.1 mm +0.045 mm (+0.0018″)
Fractional inch 13/64″ 0.2031″ / 5.159 mm +0.105 mm (+0.0041″)
Letter A 0.2340″ / 5.944 mm +0.889 mm (+0.0350″)
−0.404 mm+0.404 mm#8#10−0.14 mm#9−0.076 mm#7+0.051 mm#6+0.127 mm5.1 mm+0.045 mm13/64″+0.105 mmA +0.889 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.4 mm
Positive difference = cuts a slightly larger hole than #8. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #8
#10 0.1935 4.915 −0.14 mm
#9 0.1960 4.978 −0.076 mm
#8 0.1990 5.055 —
#7 0.2010 5.105 +0.051 mm
#6 0.2040 5.182 +0.127 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 0.1990″. See all data sources.