BenchReference / Drill sizes / P P Drill Bit Decimal inches 0.3230″
Millimeters 8.204 mm
System Letter
Nearest equivalents in other systems System Nearest drill Size Difference Metric 8.2 mm 0.3228″ / 8.2 mm −0.004 mm (−0.0002″)
Fractional inch 21/64″ 0.3281″ / 8.334 mm +0.13 mm (+0.0051″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −2.413 mm (−0.0950″)
−0.656 mm +0.656 mm P N −0.533 mm O −0.178 mm Q +0.229 mm R +0.406 mm 8.2 mm −0.004 mm 21/64″ +0.13 mm ← #1 −2.413 mm tick position = true diameter · letter neighbors above, equivalents below · window ±0.66 mm
Positive difference = cuts a slightly larger hole than P. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring letter sizes Drill Decimal in mm vs P N 0.3020 7.671 −0.533 mm O 0.3160 8.026 −0.178 mm P 0.3230 8.204 — Q 0.3320 8.433 +0.229 mm R 0.3390 8.611 +0.406 mm
← O (smaller) Q (larger) →
Compare P 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 letter size is 0.3230″. See all data sources .