Home › References › Measurement › Drill Bit Sizes 🔩 Drill Bit Sizes Reference Drill bits are available in fractional inch, letter (A–Z), number (1–80), and metric sizes. Use this chart to find inch and millimeter equivalents for any drill bit system.
Fractional Inch Size Inches mm 1/64" 0.0156 0.397 1/32" 0.0313 0.794 3/64" 0.0469 1.191 1/16" 0.0625 1.588 5/64" 0.0781 1.984 3/32" 0.0938 2.381 7/64" 0.1094 2.778 1/8" 0.1250 3.175 9/64" 0.1406 3.572 5/32" 0.1563 3.969 3/16" 0.1875 4.763 7/32" 0.2188 5.556 1/4" 0.2500 6.350 9/32" 0.2813 7.144 5/16" 0.3125 7.938 3/8" 0.3750 9.525 7/16" 0.4375 11.113 1/2" 0.5000 12.700
Letter Sizes (A–Z) Size Inches mm A 0.2340 5.944 B 0.2380 6.045 C 0.2420 6.147 D 0.2460 6.248 E 0.2500 6.350 F 0.2570 6.528 G 0.2610 6.629 H 0.2660 6.756 I 0.2720 6.909 J 0.2770 7.036 K 0.2810 7.137 L 0.2900 7.366 M 0.2950 7.493 N 0.3020 7.671 O 0.3160 8.026 P 0.3230 8.204 Q 0.3320 8.433 R 0.3390 8.611 S 0.3480 8.839 T 0.3580 9.093 U 0.3680 9.347 V 0.3770 9.576 W 0.3860 9.804 X 0.3970 10.084 Y 0.4040 10.262 Z 0.4130 10.490
Metric Sizes Size Inches 0.5 mm 0.0197 0.8 mm 0.0315 1.0 mm 0.0394 1.5 mm 0.0591 2.0 mm 0.0787 2.5 mm 0.0984 3.0 mm 0.1181 3.5 mm 0.1378 4.0 mm 0.1575 4.5 mm 0.1772 5.0 mm 0.1969 6.0 mm 0.2362 6.5 mm 0.2559 7.0 mm 0.2756 8.0 mm 0.3150 9.0 mm 0.3543 10.0 mm 0.3937 12.0 mm 0.4724