BenchReference / Drill sizes / 20 mm 20 mm Drill Decimal inches 0.7874″
Millimeters 20 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 25/32″ 0.7813″ / 19.844 mm −0.156 mm (−0.0062″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −14.209 mm (−0.5594″)
Letter Z 0.4130″ / 10.49 mm −9.51 mm (−0.3744″)
−1.6 mm +1.6 mm 20 mm 19 mm −1 mm 19.5 mm −0.5 mm 20.5 mm +0.5 mm 21 mm +1 mm 25/32″ −0.156 mm ← #1 −14.209 mm ← Z −9.51 mm tick position = true diameter · metric neighbors above, equivalents below · window ±1.6 mm
Positive difference = cuts a slightly larger hole than 20 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 20 mm 19 mm 0.7480 19 −1 mm 19.5 mm 0.7677 19.5 −0.5 mm 20 mm 0.7874 20 — 20.5 mm 0.8071 20.5 +0.5 mm 21 mm 0.8268 21 +1 mm
← 19.5 mm (smaller) 20.5 mm (larger) →
Compare 20 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 20 mm. See all data sources .