BenchReference / Drill sizes / 27/32″ 27/32″ Drill Bit Decimal inches 0.8438″
Millimeters 21.431 mm
System Fractional inch
In 64ths 54/64″
Nearest equivalents in other systems System Nearest drill Size Difference Metric 21 mm 0.8268″ / 21 mm −0.431 mm (−0.0170″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −15.64 mm (−0.6158″)
Letter Z 0.4130″ / 10.49 mm −10.941 mm (−0.4307″)
−1.714 mm +1.714 mm 27/32″ 13/16″ −0.794 mm 53/64″ −0.397 mm 55/64″ +0.397 mm 7/8″ +0.794 mm 21 mm −0.431 mm ← #1 −15.64 mm ← Z −10.941 mm tick position = true diameter · fractional neighbors above, equivalents below · window ±1.71 mm
Positive difference = cuts a slightly larger hole than 27/32″. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring fractional sizes Drill Decimal in mm vs 27/32″ 13/16″ 0.8125 20.637 −0.794 mm 53/64″ 0.8281 21.034 −0.397 mm 27/32″ 0.8438 21.431 — 55/64″ 0.8594 21.828 +0.397 mm 7/8″ 0.8750 22.225 +0.794 mm
← 53/64″ (smaller) 55/64″ (larger) →
Compare 27/32″ 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 fractional size is 0.8438″. See all data sources .