---
type: chart
title: "Drill Size Chart"
tables: 4
url: https://manufacturingprocesses.org/charts/drill-size-chart
---

# Drill Size Chart

Every number, letter, fractional and common metric drill with its decimal inch and millimeter diameter, per ANSI/ASME B94.11M.

Four drill size systems coexist on a US shop floor and none of them
supersedes the others: number drills (#1 to #80, larger number = smaller
drill), letter drills (A to Z, larger letter = larger drill), fractional
drills in 64ths of an inch, and metric drills. A single tap chart will
routinely send you to all four.

Diameters below are the nominal values from ANSI/ASME B94.11M. The
millimeter columns on the inch systems, and the inch columns on the metric
system, are computed at exactly 25.4 mm/in rather than transcribed.
Fractional decimals are computed from the fraction itself, so they are
exact — a 64th of an inch is exactly representable in decimal.

Note that letter E and 1/4 in are the same nominal diameter (0.2500 in).
That duplication is in the standard, not an error in the table.

## Number drills (#1 – #80)

| Drill | Diameter (in) | Diameter (mm) |
| --- | --- | --- |
| #80 | 0.0135 | 0.343 |
| #79 | 0.0145 | 0.368 |
| #78 | 0.016 | 0.406 |
| #77 | 0.018 | 0.457 |
| #76 | 0.02 | 0.508 |
| #75 | 0.021 | 0.533 |
| #74 | 0.0225 | 0.571 |
| #73 | 0.024 | 0.61 |
| #72 | 0.025 | 0.635 |
| #71 | 0.026 | 0.66 |
| #70 | 0.028 | 0.711 |
| #69 | 0.0292 | 0.742 |
| #68 | 0.031 | 0.787 |
| #67 | 0.032 | 0.813 |
| #66 | 0.033 | 0.838 |
| #65 | 0.035 | 0.889 |
| #64 | 0.036 | 0.914 |
| #63 | 0.037 | 0.94 |
| #62 | 0.038 | 0.965 |
| #61 | 0.039 | 0.991 |
| #60 | 0.04 | 1.016 |
| #59 | 0.041 | 1.041 |
| #58 | 0.042 | 1.067 |
| #57 | 0.043 | 1.092 |
| #56 | 0.0465 | 1.181 |
| #55 | 0.052 | 1.321 |
| #54 | 0.055 | 1.397 |
| #53 | 0.0595 | 1.511 |
| #52 | 0.0635 | 1.613 |
| #51 | 0.067 | 1.702 |
| #50 | 0.07 | 1.778 |
| #49 | 0.073 | 1.854 |
| #48 | 0.076 | 1.93 |
| #47 | 0.0785 | 1.994 |
| #46 | 0.081 | 2.057 |
| #45 | 0.082 | 2.083 |
| #44 | 0.086 | 2.184 |
| #43 | 0.089 | 2.261 |
| #42 | 0.0935 | 2.375 |
| #41 | 0.096 | 2.438 |
| #40 | 0.098 | 2.489 |
| #39 | 0.0995 | 2.527 |
| #38 | 0.1015 | 2.578 |
| #37 | 0.104 | 2.642 |
| #36 | 0.1065 | 2.705 |
| #35 | 0.11 | 2.794 |
| #34 | 0.111 | 2.819 |
| #33 | 0.113 | 2.87 |
| #32 | 0.116 | 2.946 |
| #31 | 0.12 | 3.048 |
| #30 | 0.1285 | 3.264 |
| #29 | 0.136 | 3.454 |
| #28 | 0.1405 | 3.569 |
| #27 | 0.144 | 3.658 |
| #26 | 0.147 | 3.734 |
| #25 | 0.1495 | 3.797 |
| #24 | 0.152 | 3.861 |
| #23 | 0.154 | 3.912 |
| #22 | 0.157 | 3.988 |
| #21 | 0.159 | 4.039 |
| #20 | 0.161 | 4.089 |
| #19 | 0.166 | 4.216 |
| #18 | 0.1695 | 4.305 |
| #17 | 0.173 | 4.394 |
| #16 | 0.177 | 4.496 |
| #15 | 0.18 | 4.572 |
| #14 | 0.182 | 4.623 |
| #13 | 0.185 | 4.699 |
| #12 | 0.189 | 4.801 |
| #11 | 0.191 | 4.851 |
| #10 | 0.1935 | 4.915 |
| #9 | 0.196 | 4.978 |
| #8 | 0.199 | 5.055 |
| #7 | 0.201 | 5.105 |
| #6 | 0.204 | 5.182 |
| #5 | 0.2055 | 5.22 |
| #4 | 0.209 | 5.309 |
| #3 | 0.213 | 5.41 |
| #2 | 0.221 | 5.613 |
| #1 | 0.228 | 5.791 |

## Letter drills (A – Z)

| Drill | Diameter (in) | Diameter (mm) |
| --- | --- | --- |
| A | 0.234 | 5.944 |
| B | 0.238 | 6.045 |
| C | 0.242 | 6.147 |
| D | 0.246 | 6.248 |
| E | 0.25 | 6.35 |
| F | 0.257 | 6.528 |
| G | 0.261 | 6.629 |
| H | 0.266 | 6.756 |
| I | 0.272 | 6.909 |
| J | 0.277 | 7.036 |
| K | 0.281 | 7.137 |
| L | 0.29 | 7.366 |
| M | 0.295 | 7.493 |
| N | 0.302 | 7.671 |
| O | 0.316 | 8.026 |
| P | 0.323 | 8.204 |
| Q | 0.332 | 8.433 |
| R | 0.339 | 8.611 |
| S | 0.348 | 8.839 |
| T | 0.358 | 9.093 |
| U | 0.368 | 9.347 |
| V | 0.377 | 9.576 |
| W | 0.386 | 9.804 |
| X | 0.397 | 10.084 |
| Y | 0.404 | 10.262 |
| Z | 0.413 | 10.49 |

## Fractional drills (1/64 in – 1 in, by 64ths)

| Fraction | Diameter, exact (in) | Diameter (mm) |
| --- | --- | --- |
| 1/64 | 0.015625 | 0.3969 |
| 1/32 | 0.03125 | 0.7937 |
| 3/64 | 0.046875 | 1.1906 |
| 1/16 | 0.0625 | 1.5875 |
| 5/64 | 0.078125 | 1.9844 |
| 3/32 | 0.09375 | 2.3812 |
| 7/64 | 0.109375 | 2.7781 |
| 1/8 | 0.125 | 3.175 |
| 9/64 | 0.140625 | 3.5719 |
| 5/32 | 0.15625 | 3.9688 |
| 11/64 | 0.171875 | 4.3656 |
| 3/16 | 0.1875 | 4.7625 |
| 13/64 | 0.203125 | 5.1594 |
| 7/32 | 0.21875 | 5.5562 |
| 15/64 | 0.234375 | 5.9531 |
| 1/4 | 0.25 | 6.35 |
| 17/64 | 0.265625 | 6.7469 |
| 9/32 | 0.28125 | 7.1437 |
| 19/64 | 0.296875 | 7.5406 |
| 5/16 | 0.3125 | 7.9375 |
| 21/64 | 0.328125 | 8.3344 |
| 11/32 | 0.34375 | 8.7312 |
| 23/64 | 0.359375 | 9.1281 |
| 3/8 | 0.375 | 9.525 |
| 25/64 | 0.390625 | 9.9219 |
| 13/32 | 0.40625 | 10.3187 |
| 27/64 | 0.421875 | 10.7156 |
| 7/16 | 0.4375 | 11.1125 |
| 29/64 | 0.453125 | 11.5094 |
| 15/32 | 0.46875 | 11.9062 |
| 31/64 | 0.484375 | 12.3031 |
| 1/2 | 0.5 | 12.7 |
| 33/64 | 0.515625 | 13.0969 |
| 17/32 | 0.53125 | 13.4937 |
| 35/64 | 0.546875 | 13.8906 |
| 9/16 | 0.5625 | 14.2875 |
| 37/64 | 0.578125 | 14.6844 |
| 19/32 | 0.59375 | 15.0812 |
| 39/64 | 0.609375 | 15.4781 |
| 5/8 | 0.625 | 15.875 |
| 41/64 | 0.640625 | 16.2719 |
| 21/32 | 0.65625 | 16.6687 |
| 43/64 | 0.671875 | 17.0656 |
| 11/16 | 0.6875 | 17.4625 |
| 45/64 | 0.703125 | 17.8594 |
| 23/32 | 0.71875 | 18.2562 |
| 47/64 | 0.734375 | 18.6531 |
| 3/4 | 0.75 | 19.05 |
| 49/64 | 0.765625 | 19.4469 |
| 25/32 | 0.78125 | 19.8438 |
| 51/64 | 0.796875 | 20.2406 |
| 13/16 | 0.8125 | 20.6375 |
| 53/64 | 0.828125 | 21.0344 |
| 27/32 | 0.84375 | 21.4312 |
| 55/64 | 0.859375 | 21.8281 |
| 7/8 | 0.875 | 22.225 |
| 57/64 | 0.890625 | 22.6219 |
| 29/32 | 0.90625 | 23.0187 |
| 59/64 | 0.921875 | 23.4156 |
| 15/16 | 0.9375 | 23.8125 |
| 61/64 | 0.953125 | 24.2094 |
| 31/32 | 0.96875 | 24.6062 |
| 63/64 | 0.984375 | 25.0031 |
| 1 | 1 | 25.4 |

## Common metric drills (0.5 – 13.0 mm)

| Drill | Diameter (mm) | Diameter (in) |
| --- | --- | --- |
| 0.5 mm | 0.5 | 0.0197 |
| 0.6 mm | 0.6 | 0.0236 |
| 0.7 mm | 0.7 | 0.0276 |
| 0.8 mm | 0.8 | 0.0315 |
| 0.9 mm | 0.9 | 0.0354 |
| 1 mm | 1 | 0.0394 |
| 1.1 mm | 1.1 | 0.0433 |
| 1.2 mm | 1.2 | 0.0472 |
| 1.25 mm | 1.25 | 0.0492 |
| 1.3 mm | 1.3 | 0.0512 |
| 1.4 mm | 1.4 | 0.0551 |
| 1.5 mm | 1.5 | 0.0591 |
| 1.6 mm | 1.6 | 0.063 |
| 1.7 mm | 1.7 | 0.0669 |
| 1.75 mm | 1.75 | 0.0689 |
| 1.8 mm | 1.8 | 0.0709 |
| 1.9 mm | 1.9 | 0.0748 |
| 2 mm | 2 | 0.0787 |
| 2.1 mm | 2.1 | 0.0827 |
| 2.2 mm | 2.2 | 0.0866 |
| 2.25 mm | 2.25 | 0.0886 |
| 2.3 mm | 2.3 | 0.0906 |
| 2.4 mm | 2.4 | 0.0945 |
| 2.5 mm | 2.5 | 0.0984 |
| 2.6 mm | 2.6 | 0.1024 |
| 2.7 mm | 2.7 | 0.1063 |
| 2.75 mm | 2.75 | 0.1083 |
| 2.8 mm | 2.8 | 0.1102 |
| 2.9 mm | 2.9 | 0.1142 |
| 3 mm | 3 | 0.1181 |
| 3.1 mm | 3.1 | 0.122 |
| 3.2 mm | 3.2 | 0.126 |
| 3.25 mm | 3.25 | 0.128 |
| 3.3 mm | 3.3 | 0.1299 |
| 3.4 mm | 3.4 | 0.1339 |
| 3.5 mm | 3.5 | 0.1378 |
| 3.6 mm | 3.6 | 0.1417 |
| 3.7 mm | 3.7 | 0.1457 |
| 3.75 mm | 3.75 | 0.1476 |
| 3.8 mm | 3.8 | 0.1496 |
| 3.9 mm | 3.9 | 0.1535 |
| 4 mm | 4 | 0.1575 |
| 4.1 mm | 4.1 | 0.1614 |
| 4.2 mm | 4.2 | 0.1654 |
| 4.25 mm | 4.25 | 0.1673 |
| 4.3 mm | 4.3 | 0.1693 |
| 4.4 mm | 4.4 | 0.1732 |
| 4.5 mm | 4.5 | 0.1772 |
| 4.6 mm | 4.6 | 0.1811 |
| 4.7 mm | 4.7 | 0.185 |
| 4.75 mm | 4.75 | 0.187 |
| 4.8 mm | 4.8 | 0.189 |
| 4.9 mm | 4.9 | 0.1929 |
| 5 mm | 5 | 0.1969 |
| 5.1 mm | 5.1 | 0.2008 |
| 5.2 mm | 5.2 | 0.2047 |
| 5.25 mm | 5.25 | 0.2067 |
| 5.3 mm | 5.3 | 0.2087 |
| 5.4 mm | 5.4 | 0.2126 |
| 5.5 mm | 5.5 | 0.2165 |
| 5.6 mm | 5.6 | 0.2205 |
| 5.7 mm | 5.7 | 0.2244 |
| 5.75 mm | 5.75 | 0.2264 |
| 5.8 mm | 5.8 | 0.2283 |
| 5.9 mm | 5.9 | 0.2323 |
| 6 mm | 6 | 0.2362 |
| 6.1 mm | 6.1 | 0.2402 |
| 6.2 mm | 6.2 | 0.2441 |
| 6.25 mm | 6.25 | 0.2461 |
| 6.3 mm | 6.3 | 0.248 |
| 6.4 mm | 6.4 | 0.252 |
| 6.5 mm | 6.5 | 0.2559 |
| 6.6 mm | 6.6 | 0.2598 |
| 6.7 mm | 6.7 | 0.2638 |
| 6.75 mm | 6.75 | 0.2657 |
| 6.8 mm | 6.8 | 0.2677 |
| 6.9 mm | 6.9 | 0.2717 |
| 7 mm | 7 | 0.2756 |
| 7.1 mm | 7.1 | 0.2795 |
| 7.2 mm | 7.2 | 0.2835 |
| 7.25 mm | 7.25 | 0.2854 |
| 7.3 mm | 7.3 | 0.2874 |
| 7.4 mm | 7.4 | 0.2913 |
| 7.5 mm | 7.5 | 0.2953 |
| 7.6 mm | 7.6 | 0.2992 |
| 7.7 mm | 7.7 | 0.3031 |
| 7.75 mm | 7.75 | 0.3051 |
| 7.8 mm | 7.8 | 0.3071 |
| 7.9 mm | 7.9 | 0.311 |
| 8 mm | 8 | 0.315 |
| 8.25 mm | 8.25 | 0.3248 |
| 8.5 mm | 8.5 | 0.3346 |
| 8.75 mm | 8.75 | 0.3445 |
| 9 mm | 9 | 0.3543 |
| 9.25 mm | 9.25 | 0.3642 |
| 9.5 mm | 9.5 | 0.374 |
| 9.75 mm | 9.75 | 0.3839 |
| 10 mm | 10 | 0.3937 |
| 10.5 mm | 10.5 | 0.4134 |
| 11 mm | 11 | 0.4331 |
| 11.5 mm | 11.5 | 0.4528 |
| 12 mm | 12 | 0.4724 |
| 12.5 mm | 12.5 | 0.4921 |
| 13 mm | 13 | 0.5118 |

## Notes

**Letter K is 0.2810 in, not 0.2811 in.** Engineers Edge publishes 0.2811;
Wikipedia and *Machinery's Handbook* give 0.2810, which is the value in
ASME B94.11M and in every drill manufacturer's catalog. The Engineers Edge
figure looks like a transcription artefact from the adjacent 9/32 = 0.28125
row. The 0.0001 in difference sits below drill manufacturing tolerance, so
it will never matter at the machine — but this chart publishes four-place
decimals, so it matters here.

**Several published fractional decimals are truncated rather than rounded.**
Engineers Edge shows 11/32 as .3437 (correctly .3438), 15/32 as .4687
(.4688), 19/32 as .5937 (.5938), 23/32 as .7187 (.7188), 27/32 as .8437
(.8438) and 31/32 as .9687 (.9688). Because this chart computes fractional
decimals from the fraction, none of that propagates.

**Shop-floor names are not a second size.** Machinists call fractional
drills by an abbreviated decimal — 27/64 is "a four-twenty-one drill", 1/16
is "a sixty-two". That shorthand is inconsistent (it rounds in some places
and follows tradition in others), so it is deliberately not tabulated here.
The exact decimal is the one to work from.

All 80 number drills and all 26 letter drills were cross-checked cell by
cell against two independent sources.

## FAQ

### What size is a #7 drill?

A #7 drill is 0.2010 in (5.105 mm). It is the standard tap drill for a 1/4-20 UNC thread at roughly 75% engagement.

### Do number drills get bigger or smaller as the number goes up?

Smaller. #1 is the largest at 0.2280 in and #80 is the smallest at 0.0135 in. Letter drills run the other way: A is the smallest at 0.2340 in and Z the largest at 0.4130 in.

### What is the metric equivalent of a 1/4 in drill?

1/4 in is exactly 6.350 mm. The nearest stocked metric drills are 6.3 mm (0.2480 in) and 6.4 mm (0.2520 in), so neither is an exact substitute.

### Why do letter E and 1/4 in have the same diameter?

Because they genuinely do: both are 0.2500 in. The letter and fractional series overlap in places and ASME B94.11M lists both designations. It is a duplicate name, not a duplicate size.

### What is the largest number drill and the smallest letter drill?

The largest number drill is #1 at 0.2280 in; the smallest letter drill is A at 0.2340 in. The series are contiguous, so the letter drills pick up where the number drills leave off.

### How precise are these decimals?

Number and letter drill diameters are the nominal values from ANSI/ASME B94.11M, cross-checked cell by cell against two sources. Fractional decimals are computed exactly from the fraction, and the metric-to-inch conversions use exactly 25.4 mm/in.

## Sources

- [Wikipedia — Drill bit sizes (sourced to ASME B94.11M)](https://en.wikipedia.org/wiki/Drill_bit_sizes)
- [Engineers Edge — Machinist Drill Bit Size Table (ANSI/ASME B94.11M-1993)](https://www.engineersedge.com/drill_sizes.htm)

## Related processes

- [CNC Milling](https://manufacturingprocesses.org/processes/cutting/cnc-milling.md)
- [CNC Machining](https://manufacturingprocesses.org/processes/cutting/cnc-machining.md)
- [CNC Turning](https://manufacturingprocesses.org/processes/cutting/cnc-turning.md)

## Related charts

- [Tap Drill Chart](https://manufacturingprocesses.org/charts/tap-drill-chart.md)
- [Thread Size Chart](https://manufacturingprocesses.org/charts/thread-size-chart.md)

---

*Source: [Manufacturing Processes](https://manufacturingprocesses.org/charts/drill-size-chart)*

*Last updated: August 11, 2026*