BenchReference / Drill sizes / 4 mm 4 mm Drill Decimal inches 0.1575″
Millimeters 4 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 5/32″ 0.1563″ / 3.969 mm −0.031 mm (−0.0012″)
Number (wire gauge) #22 0.1570″ / 3.988 mm −0.012 mm (−0.0005″)
Letter A 0.2340″ / 5.944 mm +1.944 mm (+0.0765″)
−0.32 mm +0.32 mm 4 mm 3.8 mm −0.2 mm 3.9 mm −0.1 mm 4.1 mm +0.1 mm 4.2 mm +0.2 mm 5/32″ −0.031 mm #22 −0.012 mm A +1.944 mm → tick position = true diameter · metric neighbors above, equivalents below · window ±0.32 mm
Positive difference = cuts a slightly larger hole than 4 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring metric sizes Drill Decimal in mm vs 4 mm 3.8 mm 0.1496 3.8 −0.2 mm 3.9 mm 0.1535 3.9 −0.1 mm 4 mm 0.1575 4 — 4.1 mm 0.1614 4.1 +0.1 mm 4.2 mm 0.1654 4.2 +0.2 mm
← 3.9 mm (smaller) 4.1 mm (larger) →
Compare 4 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 4 mm. See all data sources .