Complete Drill Bit Size Chart
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Your comprehensive reference for fractional, number, letter, and metric drill bit sizes. Includes tap drill sizes, clearance holes, and pilot hole recommendations.
Photo via Unsplash
Your comprehensive reference for fractional, number, letter, and metric drill bit sizes. Includes tap drill sizes, clearance holes, and pilot hole recommendations.
Standard drill bits come in four series: fractional (1/64″ to 1″ in 1/64″ steps), number/wire-gauge (#1 = 0.228″ down to #80 = 0.0135″), letter (A = 0.234″ to Z = 0.413″), and metric (commonly 1–13 mm in 0.5 mm steps). For tapping a 1/4″-20 thread use a #7 (0.201″) bit; for a clearance hole use 17/64″ (0.266″). The chart below lists all 282 standard sizes with decimal and millimeter equivalents, search or filter by series.
Updated 2026. The fractional drill bit sizes in a standard set run from 1/16 inch to 1/2 inch in 64ths, and the table converts each to decimal inches and millimeters. The full number, letter and metric charts follow below.
| Drill Bit Size | Decimal (in) | Millimeters |
|---|---|---|
| 1/16" | 0.0625" | 1.59 mm |
| 5/64" | 0.0781" | 1.98 mm |
| 3/32" | 0.0938" | 2.38 mm |
| 7/64" | 0.1094" | 2.78 mm |
| 1/8" | 0.1250" | 3.17 mm |
| 9/64" | 0.1406" | 3.57 mm |
| 5/32" | 0.1562" | 3.97 mm |
| 11/64" | 0.1719" | 4.37 mm |
| 3/16" | 0.1875" | 4.76 mm |
| 13/64" | 0.2031" | 5.16 mm |
| 7/32" | 0.2188" | 5.56 mm |
| 15/64" | 0.2344" | 5.95 mm |
| 1/4" | 0.2500" | 6.35 mm |
| 17/64" | 0.2656" | 6.75 mm |
| 9/32" | 0.2812" | 7.14 mm |
| 19/64" | 0.2969" | 7.54 mm |
| 5/16" | 0.3125" | 7.94 mm |
| 11/32" | 0.3438" | 8.73 mm |
| 3/8" | 0.3750" | 9.52 mm |
| 13/32" | 0.4062" | 10.32 mm |
| 7/16" | 0.4375" | 11.11 mm |
| 15/32" | 0.4688" | 11.91 mm |
| 1/2" | 0.5000" | 12.70 mm |
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Metric equivalents to know: 3 mm is 0.118 in, 4 mm is 0.157 in, 5 mm is 0.197 in, 6 mm is 0.236 in, 8 mm is 0.315 in and 10 mm is 0.394 in. No fractional bit is an exact match for a metric size, so use the closest size only for clearance holes.
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| Size | Decimal (in) | Millimeters | Type |
|---|
Use these drill sizes before tapping threads. Based on 75% thread engagement (standard practice). To size a tap drill for any thread and engagement percentage, use our drill and tap calculator.
| Thread | Tap Drill | Decimal |
|---|---|---|
| 4-40 | #43 | 0.089" |
| 6-32 | #36 | 0.1065" |
| 8-32 | #29 | 0.136" |
| 10-24 | #25 | 0.1495" |
| 10-32 | #21 | 0.159" |
| 1/4-20 | #7 | 0.201" |
| 5/16-18 | F | 0.257" |
| 3/8-16 | 5/16" | 0.3125" |
| 7/16-14 | U | 0.368" |
| 1/2-13 | 27/64" | 0.4219" |
| 5/8-11 | 17/32" | 0.5313" |
| 3/4-10 | 21/32" | 0.6563" |
| Thread | Tap Drill | Decimal |
|---|---|---|
| M3 x 0.5 | 2.5mm | 0.098" |
| M4 x 0.7 | 3.3mm | 0.130" |
| M5 x 0.8 | 4.2mm | 0.165" |
| M6 x 1.0 | 5.0mm | 0.197" |
| M8 x 1.25 | 6.8mm | 0.268" |
| M10 x 1.5 | 8.5mm | 0.335" |
| M12 x 1.75 | 10.2mm | 0.402" |
| M14 x 2.0 | 12.0mm | 0.472" |
| M16 x 2.0 | 14.0mm | 0.551" |
| M20 x 2.5 | 17.5mm | 0.689" |
A 115-piece index holds every fractional, letter, and number size in the tables above in one case.
Better Pick
Drill America 115-Piece M35 Cobalt Drill Bit Set
Fractional + letter + number in cobalt for hard metals
Under $500
Check Price on Amazon
Good Pick
Drill America 115-Piece HSS Black Oxide Set
1/16" to 1/2", A to Z, #1 to #60: this whole chart
Under $250
Check Price on Amazon
Everyday Pick
DEWALT 29-Piece Titanium Pilot Point Set (DW1369)
The everyday fractional range
Under $250
Check Price on Amazon
As an Amazon Associate, WorkshopCalc earns from qualifying purchases. Prices are approximate and can change.
Use these drill sizes when the bolt needs to pass through freely (not threaded).
| Bolt Size | Close Fit | Free Fit |
|---|---|---|
| #4 | 1/8" | 9/64" |
| #6 | 9/64" | 5/32" |
| #8 | 11/64" | 3/16" |
| #10 | 13/64" | 7/32" |
| 1/4" | 17/64" | 9/32" |
| 5/16" | 21/64" | 11/32" |
| 3/8" | 25/64" | 13/32" |
| 7/16" | 29/64" | 15/32" |
| 1/2" | 17/32" | 9/16" |
| 5/8" | 21/32" | 11/16" |
| 3/4" | 25/32" | 13/16" |
| Bolt Size | Close Fit | Free Fit |
|---|---|---|
| M3 | 3.2mm | 3.4mm |
| M4 | 4.3mm | 4.5mm |
| M5 | 5.3mm | 5.5mm |
| M6 | 6.4mm | 6.6mm |
| M8 | 8.4mm | 9.0mm |
| M10 | 10.5mm | 11.0mm |
| M12 | 13.0mm | 14.0mm |
| M14 | 15.0mm | 16.0mm |
| M16 | 17.0mm | 18.0mm |
| M20 | 21.0mm | 22.0mm |
Pilot holes prevent splitting and make driving easier. Use smaller size for softwood, larger for hardwood. See the full pilot hole chart for exact drill sizes by screw gauge.
| Screw Size | Softwood Pilot | Hardwood Pilot | Shank Hole | Countersink |
|---|---|---|---|---|
| #2 | 1/16" | 1/16" | 3/32" | 3/16" |
| #3 | 1/16" | 5/64" | 7/64" | 1/4" |
| #4 | 1/16" | 5/64" | 7/64" | 1/4" |
| #5 | 5/64" | 3/32" | 1/8" | 1/4" |
| #6 | 5/64" | 3/32" | 9/64" | 5/16" |
| #7 | 3/32" | 7/64" | 5/32" | 5/16" |
| #8 | 3/32" | 7/64" | 11/64" | 3/8" |
| #9 | 7/64" | 1/8" | 3/16" | 3/8" |
| #10 | 7/64" | 1/8" | 3/16" | 3/8" |
| #12 | 1/8" | 9/64" | 7/32" | 7/16" |
| #14 | 9/64" | 5/32" | 1/4" | 1/2" |
Every standard drill size, listed by series with decimal-inch and millimeter equivalents. Fractional, number (wire gauge), and letter twist drill sizes follow the ANSI/ASME B94.11M standard. Prefer to search? Use the interactive table at the top of this page. Once you have chosen a bit, match it to the right RPM with our drill speed chart.
All 64 fractional-inch sizes in 1/64" steps, per ANSI/ASME B94.11M.
| Size | Decimal (in) | Millimeters |
|---|---|---|
| 1/64" | 0.0156 | 0.397 |
| 1/32" | 0.0312 | 0.794 |
| 3/64" | 0.0469 | 1.191 |
| 1/16" | 0.0625 | 1.587 |
| 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" | 0.1562 | 3.969 |
| 11/64" | 0.1719 | 4.366 |
| 3/16" | 0.1875 | 4.762 |
| 13/64" | 0.2031 | 5.159 |
| 7/32" | 0.2188 | 5.556 |
| 15/64" | 0.2344 | 5.953 |
| 1/4" | 0.2500 | 6.350 |
| 17/64" | 0.2656 | 6.747 |
| 9/32" | 0.2812 | 7.144 |
| 19/64" | 0.2969 | 7.541 |
| 5/16" | 0.3125 | 7.938 |
| 21/64" | 0.3281 | 8.334 |
| 11/32" | 0.3438 | 8.731 |
| 23/64" | 0.3594 | 9.128 |
| 3/8" | 0.3750 | 9.525 |
| 25/64" | 0.3906 | 9.922 |
| 13/32" | 0.4062 | 10.319 |
| 27/64" | 0.4219 | 10.716 |
| 7/16" | 0.4375 | 11.112 |
| 29/64" | 0.4531 | 11.509 |
| 15/32" | 0.4688 | 11.906 |
| 31/64" | 0.4844 | 12.303 |
| 1/2" | 0.5000 | 12.700 |
| 33/64" | 0.5156 | 13.097 |
| 17/32" | 0.5312 | 13.494 |
| 35/64" | 0.5469 | 13.891 |
| 9/16" | 0.5625 | 14.287 |
| 37/64" | 0.5781 | 14.684 |
| 19/32" | 0.5938 | 15.081 |
| 39/64" | 0.6094 | 15.478 |
| 5/8" | 0.6250 | 15.875 |
| 41/64" | 0.6406 | 16.272 |
| 21/32" | 0.6562 | 16.669 |
| 43/64" | 0.6719 | 17.066 |
| 11/16" | 0.6875 | 17.462 |
| 45/64" | 0.7031 | 17.859 |
| 23/32" | 0.7188 | 18.256 |
| 47/64" | 0.7344 | 18.653 |
| 3/4" | 0.7500 | 19.050 |
| 49/64" | 0.7656 | 19.447 |
| 25/32" | 0.7812 | 19.844 |
| 51/64" | 0.7969 | 20.241 |
| 13/16" | 0.8125 | 20.637 |
| 53/64" | 0.8281 | 21.034 |
| 27/32" | 0.8438 | 21.431 |
| 55/64" | 0.8594 | 21.828 |
| 7/8" | 0.8750 | 22.225 |
| 57/64" | 0.8906 | 22.622 |
| 29/32" | 0.9062 | 23.019 |
| 59/64" | 0.9219 | 23.416 |
| 15/16" | 0.9375 | 23.812 |
| 61/64" | 0.9531 | 24.209 |
| 31/32" | 0.9688 | 24.606 |
| 63/64" | 0.9844 | 25.003 |
| 1" | 1.0000 | 25.400 |
Number sizes run from #1 (largest, 0.2280") to #80 (smallest, 0.0135"), per ANSI/ASME B94.11M. Listed largest to smallest.
| Size | Decimal (in) | Millimeters |
|---|---|---|
| #1 | 0.2280 | 5.791 |
| #2 | 0.2210 | 5.613 |
| #3 | 0.2130 | 5.410 |
| #4 | 0.2090 | 5.309 |
| #5 | 0.2055 | 5.220 |
| #6 | 0.2040 | 5.182 |
| #7 | 0.2010 | 5.105 |
| #8 | 0.1990 | 5.055 |
| #9 | 0.1960 | 4.978 |
| #10 | 0.1935 | 4.915 |
| #11 | 0.1910 | 4.851 |
| #12 | 0.1890 | 4.801 |
| #13 | 0.1850 | 4.699 |
| #14 | 0.1820 | 4.623 |
| #15 | 0.1800 | 4.572 |
| #16 | 0.1770 | 4.496 |
| #17 | 0.1730 | 4.394 |
| #18 | 0.1695 | 4.305 |
| #19 | 0.1660 | 4.216 |
| #20 | 0.1610 | 4.089 |
| #21 | 0.1590 | 4.039 |
| #22 | 0.1570 | 3.988 |
| #23 | 0.1540 | 3.912 |
| #24 | 0.1520 | 3.861 |
| #25 | 0.1495 | 3.797 |
| #26 | 0.1470 | 3.734 |
| #27 | 0.1440 | 3.658 |
| #28 | 0.1405 | 3.569 |
| #29 | 0.1360 | 3.454 |
| #30 | 0.1285 | 3.264 |
| #31 | 0.1200 | 3.048 |
| #32 | 0.1160 | 2.946 |
| #33 | 0.1130 | 2.870 |
| #34 | 0.1110 | 2.819 |
| #35 | 0.1100 | 2.794 |
| #36 | 0.1065 | 2.705 |
| #37 | 0.1040 | 2.642 |
| #38 | 0.1015 | 2.578 |
| #39 | 0.0995 | 2.527 |
| #40 | 0.0980 | 2.489 |
| #41 | 0.0960 | 2.438 |
| #42 | 0.0935 | 2.375 |
| #43 | 0.0890 | 2.261 |
| #44 | 0.0860 | 2.184 |
| #45 | 0.0820 | 2.083 |
| #46 | 0.0810 | 2.057 |
| #47 | 0.0785 | 1.994 |
| #48 | 0.0760 | 1.930 |
| #49 | 0.0730 | 1.854 |
| #50 | 0.0700 | 1.778 |
| #51 | 0.0670 | 1.702 |
| #52 | 0.0635 | 1.613 |
| #53 | 0.0595 | 1.511 |
| #54 | 0.0550 | 1.397 |
| #55 | 0.0520 | 1.321 |
| #56 | 0.0465 | 1.181 |
| #57 | 0.0430 | 1.092 |
| #58 | 0.0420 | 1.067 |
| #59 | 0.0410 | 1.041 |
| #60 | 0.0400 | 1.016 |
| #61 | 0.0390 | 0.991 |
| #62 | 0.0380 | 0.965 |
| #63 | 0.0370 | 0.940 |
| #64 | 0.0360 | 0.914 |
| #65 | 0.0350 | 0.889 |
| #66 | 0.0330 | 0.838 |
| #67 | 0.0320 | 0.813 |
| #68 | 0.0310 | 0.787 |
| #69 | 0.0292 | 0.742 |
| #70 | 0.0280 | 0.711 |
| #71 | 0.0260 | 0.660 |
| #72 | 0.0250 | 0.635 |
| #73 | 0.0240 | 0.610 |
| #74 | 0.0225 | 0.571 |
| #75 | 0.0210 | 0.533 |
| #76 | 0.0200 | 0.508 |
| #77 | 0.0180 | 0.457 |
| #78 | 0.0160 | 0.406 |
| #79 | 0.0145 | 0.368 |
| #80 | 0.0135 | 0.343 |
Letter sizes run from A (smallest, 0.234") to Z (largest, 0.413"), per ANSI/ASME B94.11M.
| Size | Decimal (in) | Millimeters |
|---|---|---|
| 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 |
Common metric sizes in 0.1mm and 0.5mm steps. Divide millimeters by 25.4 for the decimal-inch equivalent.
| Size | Decimal (in) | Millimeters |
|---|---|---|
| 0.5mm | 0.0197 | 0.500 |
| 0.6mm | 0.0236 | 0.600 |
| 0.7mm | 0.0276 | 0.700 |
| 0.8mm | 0.0315 | 0.800 |
| 0.9mm | 0.0354 | 0.900 |
| 1mm | 0.0394 | 1.000 |
| 1.1mm | 0.0433 | 1.100 |
| 1.2mm | 0.0472 | 1.200 |
| 1.3mm | 0.0512 | 1.300 |
| 1.4mm | 0.0551 | 1.400 |
| 1.5mm | 0.0591 | 1.500 |
| 1.6mm | 0.0630 | 1.600 |
| 1.7mm | 0.0669 | 1.700 |
| 1.8mm | 0.0709 | 1.800 |
| 1.9mm | 0.0748 | 1.900 |
| 2mm | 0.0787 | 2.000 |
| 2.1mm | 0.0827 | 2.100 |
| 2.2mm | 0.0866 | 2.200 |
| 2.3mm | 0.0906 | 2.300 |
| 2.4mm | 0.0945 | 2.400 |
| 2.5mm | 0.0984 | 2.500 |
| 2.6mm | 0.1024 | 2.600 |
| 2.7mm | 0.1063 | 2.700 |
| 2.8mm | 0.1102 | 2.800 |
| 2.9mm | 0.1142 | 2.900 |
| 3mm | 0.1181 | 3.000 |
| 3.1mm | 0.1220 | 3.100 |
| 3.2mm | 0.1260 | 3.200 |
| 3.3mm | 0.1299 | 3.300 |
| 3.4mm | 0.1339 | 3.400 |
| 3.5mm | 0.1378 | 3.500 |
| 3.6mm | 0.1417 | 3.600 |
| 3.7mm | 0.1457 | 3.700 |
| 3.8mm | 0.1496 | 3.800 |
| 3.9mm | 0.1535 | 3.900 |
| 4mm | 0.1575 | 4.000 |
| 4.1mm | 0.1614 | 4.100 |
| 4.2mm | 0.1654 | 4.200 |
| 4.3mm | 0.1693 | 4.300 |
| 4.4mm | 0.1732 | 4.400 |
| 4.5mm | 0.1772 | 4.500 |
| 4.6mm | 0.1811 | 4.600 |
| 4.7mm | 0.1850 | 4.700 |
| 4.8mm | 0.1890 | 4.800 |
| 4.9mm | 0.1929 | 4.900 |
| 5mm | 0.1969 | 5.000 |
| 5.1mm | 0.2008 | 5.100 |
| 5.2mm | 0.2047 | 5.200 |
| 5.3mm | 0.2087 | 5.300 |
| 5.4mm | 0.2126 | 5.400 |
| 5.5mm | 0.2165 | 5.500 |
| 5.6mm | 0.2205 | 5.600 |
| 5.7mm | 0.2244 | 5.700 |
| 5.8mm | 0.2283 | 5.800 |
| 5.9mm | 0.2323 | 5.900 |
| 6mm | 0.2362 | 6.000 |
| 6.2mm | 0.2441 | 6.200 |
| 6.4mm | 0.2520 | 6.400 |
| 6.5mm | 0.2559 | 6.500 |
| 6.6mm | 0.2598 | 6.600 |
| 6.8mm | 0.2677 | 6.800 |
| 7mm | 0.2756 | 7.000 |
| 7.2mm | 0.2835 | 7.200 |
| 7.4mm | 0.2913 | 7.400 |
| 7.5mm | 0.2953 | 7.500 |
| 7.6mm | 0.2992 | 7.600 |
| 7.8mm | 0.3071 | 7.800 |
| 8mm | 0.3150 | 8.000 |
| 8.2mm | 0.3228 | 8.200 |
| 8.4mm | 0.3307 | 8.400 |
| 8.5mm | 0.3346 | 8.500 |
| 8.6mm | 0.3386 | 8.600 |
| 8.8mm | 0.3465 | 8.800 |
| 9mm | 0.3543 | 9.000 |
| 9.2mm | 0.3622 | 9.200 |
| 9.4mm | 0.3701 | 9.400 |
| 9.5mm | 0.3740 | 9.500 |
| 9.6mm | 0.3780 | 9.600 |
| 9.8mm | 0.3858 | 9.800 |
| 10mm | 0.3937 | 10.000 |
| 10.2mm | 0.4016 | 10.200 |
| 10.5mm | 0.4134 | 10.500 |
| 10.8mm | 0.4252 | 10.800 |
| 11mm | 0.4331 | 11.000 |
| 11.5mm | 0.4528 | 11.500 |
| 12mm | 0.4724 | 12.000 |
| 12.5mm | 0.4921 | 12.500 |
| 13mm | 0.5118 | 13.000 |
| 13.5mm | 0.5315 | 13.500 |
| 14mm | 0.5512 | 14.000 |
| 14.5mm | 0.5709 | 14.500 |
| 15mm | 0.5906 | 15.000 |
| 15.5mm | 0.6102 | 15.500 |
| 16mm | 0.6299 | 16.000 |
| 16.5mm | 0.6496 | 16.500 |
| 17mm | 0.6693 | 17.000 |
| 17.5mm | 0.6890 | 17.500 |
| 18mm | 0.7087 | 18.000 |
| 18.5mm | 0.7283 | 18.500 |
| 19mm | 0.7480 | 19.000 |
| 19.5mm | 0.7677 | 19.500 |
| 20mm | 0.7874 | 20.000 |
| 20.5mm | 0.8071 | 20.500 |
| 21mm | 0.8268 | 21.000 |
| 21.5mm | 0.8465 | 21.500 |
| 22mm | 0.8661 | 22.000 |
| 22.5mm | 0.8858 | 22.500 |
| 23mm | 0.9055 | 23.000 |
| 23.5mm | 0.9252 | 23.500 |
| 24mm | 0.9449 | 24.000 |
| 24.5mm | 0.9646 | 24.500 |
| 25mm | 0.9843 | 25.000 |
The right drill bit set saves hours of frustration. These are the picks we trust for accurate hole sizing across wood, metal, and masonry. All links are affiliate links, we may earn a commission at no cost to you.
Number drill bits range from #1 (0.228") to #80 (0.0135"), with higher numbers being smaller. Letter drill bits range from A (0.234") to Z (0.413"), with later letters being larger. Together they fill in the gaps between fractional sizes, providing more precise sizing options for tap drills and close-tolerance work.
To convert metric drill sizes to inches, divide the millimeter size by 25.4. For example, a 6mm drill bit equals 6 / 25.4 = 0.236 inches. Our chart includes both metric and imperial equivalents for easy reference. For quick mental math, 25mm is almost exactly 1 inch, and 1mm is about 0.040 inches.
For softwood like pine or cedar, use a pilot hole about 60-70% of the screw's root diameter. For hardwood like oak or maple, use 80-90%. For example, a #8 wood screw typically needs a 3/32" pilot hole in softwood or 7/64" in hardwood. Always drill a shank hole the same diameter as the screw shank where the non-threaded portion will sit.
A tap drill creates a hole that will be threaded with a tap. The correct size depends on the thread size and desired engagement percentage. Standard practice is 75% thread engagement, which provides near-full strength (about 98%) while being much easier to tap than 100%. Use our tap drill chart above or the formula: Tap Drill = Major Diameter - (1 / TPI) for inch threads, or Major Diameter - Pitch for metric.
Standard drill bit sizes come in four series defined by ANSI/ASME B94.11M: fractional-inch sizes from 1/64" to 1" in 1/64" steps, number (wire gauge) sizes from #80 (0.0135") to #1 (0.228"), letter sizes from A (0.234") to Z (0.413"), and metric sizes commonly from 0.5mm to 25mm. Together that is 282 standard sizes, all listed in the chart on this page.
The most commonly used drill bit sizes are the fractional sizes found in a standard 1/16" to 1/2" set: 1/16, 5/64, 3/32, 7/64, 1/8, 9/64, 5/32, 3/16, 7/32, 1/4, 5/16, 3/8, 7/16, and 1/2 inch. For everyday tasks, 1/8", 3/16", 1/4", and 3/8" see the most use. In metric shops, the equivalent workhorse sizes are 3mm, 5mm, 6mm, 8mm, and 10mm.
A drill bit size chart lists each size designation (such as 1/4", #7, F, or 6mm) alongside its decimal-inch and millimeter equivalent. To use it, find the hole diameter you need in the decimal or millimeter column, then read across to see which bit gives you that diameter. The decimal equivalent is what matters: a #7 bit (0.201"), a 5.1mm bit (0.2008"), and a 13/64" bit (0.2031") are nearly interchangeable for most work.
Yes. This page includes a complete printable drill bit size chart with all 282 standard sizes organized by series: fractional, number, letter, and metric, each with decimal-inch and millimeter equivalents. Use your browser's print function to print the by-series tables for your shop wall.
A 1/4 inch drill bit is 6.35 mm (0.250 in). The closest standard metric bit is 6 mm, which is 0.236 inch and slightly smaller, so a 6 mm bit will not make a hole big enough for a 1/4 inch bolt.
The closest fractional drill bit to 5 mm (0.197 in) is 13/64 inch (0.203 in, 5.16 mm). The 3/16 inch bit (4.76 mm) is slightly small. Use a true 5 mm bit when a precise hole is needed, such as for a press fit or tap drill.
A 3/8 inch drill bit is 9.53 mm (0.375 in). The closest metric bit is 9.5 mm, and 10 mm (0.394 in) is a loose fit for a 3/8 inch bolt.