BenchReference / Drill sizes / 10 mm 10 mm Drill Decimal inches 0.3937″
Millimeters 10 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 25/64″ 0.3906″ / 9.922 mm −0.078 mm (−0.0031″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −4.209 mm (−0.1657″)
Letter X 0.3970″ / 10.084 mm +0.084 mm (+0.0033″)
−0.8 mm +0.8 mm 10 mm 9.8 mm −0.2 mm 9.9 mm −0.1 mm 10.1 mm +0.1 mm 10.2 mm +0.2 mm 25/64″ −0.078 mm X +0.084 mm ← #1 −4.209 mm tick position = true diameter · metric neighbors above, equivalents below · window ±0.8 mm
Positive difference = cuts a slightly larger hole than 10 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Clearance drill for Neighboring metric sizes Drill Decimal in mm vs 10 mm 9.8 mm 0.3858 9.8 −0.2 mm 9.9 mm 0.3898 9.9 −0.1 mm 10 mm 0.3937 10 — 10.1 mm 0.3976 10.1 +0.1 mm 10.2 mm 0.4016 10.2 +0.2 mm
← 9.9 mm (smaller) 10.1 mm (larger) →
Compare 10 mm 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 metric size is 10 mm. See all data sources .