BenchReference / Drill sizes / 10.9 mm 10.9 mm Drill Decimal inches 0.4291″
Millimeters 10.9 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 27/64″ 0.4219″ / 10.716 mm −0.184 mm (−0.0073″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −5.109 mm (−0.2011″)
Letter Z 0.4130″ / 10.49 mm −0.41 mm (−0.0161″)
−0.872 mm +0.872 mm 10.9 mm 10.7 mm −0.2 mm 10.8 mm −0.1 mm 11 mm +0.1 mm 11.1 mm +0.2 mm Z −0.41 mm 27/64″ −0.184 mm ← #1 −5.109 mm tick position = true diameter · metric neighbors above, equivalents below · window ±0.87 mm
Positive difference = cuts a slightly larger hole than 10.9 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring metric sizes Drill Decimal in mm vs 10.9 mm 10.7 mm 0.4213 10.7 −0.2 mm 10.8 mm 0.4252 10.8 −0.1 mm 10.9 mm 0.4291 10.9 — 11 mm 0.4331 11 +0.1 mm 11.1 mm 0.4370 11.1 +0.2 mm
← 10.8 mm (smaller) 11 mm (larger) →
Compare 10.9 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 10.9 mm. See all data sources .