BenchReference / Drill sizes / 63/64″ 63/64″ Drill Bit Decimal inches 0.9844″
Millimeters 25.003 mm
System Fractional inch
Nearest equivalents in other systems System Nearest drill Size Difference Metric 21 mm 0.8268″ / 21 mm −4.003 mm (−0.1576″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −19.212 mm (−0.7564″)
Letter Z 0.4130″ / 10.49 mm −14.513 mm (−0.5714″)
−2 mm +2 mm 63/64″ 61/64″ −0.794 mm 31/32″ −0.397 mm 1″ +0.397 mm ← 21 mm −4.003 mm ← #1 −19.212 mm tick position = true diameter · fractional neighbors above, equivalents below · window ±2.0 mm
Positive difference = cuts a slightly larger hole than 63/64″. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring fractional sizes Drill Decimal in mm vs 63/64″ 61/64″ 0.9531 24.209 −0.794 mm 31/32″ 0.9688 24.606 −0.397 mm 63/64″ 0.9844 25.003 — 1″ 1.0000 25.4 +0.397 mm
← 31/32″ (smaller) 1″ (larger) →
Compare 63/64″ 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 0.9844″. See all data sources .