BenchReference

#40 Drill Bit

Decimal inches 0.0980″
Millimeters 2.489 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 2.5 mm 0.0984″ / 2.5 mm +0.011 mm (+0.0004″)
Fractional inch 3/32″ 0.0938″ / 2.381 mm −0.108 mm (−0.0043″)
Letter A 0.2340″ / 5.944 mm +3.454 mm (+0.1360″)
−0.199 mm+0.199 mm#40#42−0.114 mm#41−0.051 mm#39+0.038 mm#38+0.089 mm3/32″−0.108 mm2.5 mm+0.011 mmA +3.454 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.2 mm
Positive difference = cuts a slightly larger hole than #40. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #40
#42 0.0935 2.375 −0.114 mm
#41 0.0960 2.438 −0.051 mm
#40 0.0980 2.489 —
#39 0.0995 2.527 +0.038 mm
#38 0.1015 2.578 +0.089 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 0.0980″. See all data sources.