Drill series · Fractional
Fractional Drill Sizes — Decimal Inch and Millimetre Chart
https://shopmath.org/drills/fractional · data verified August 1, 2026
The fractional drill sizes run from 1/64" at 0.0156 in (0.397 mm) to 1" at 1.0000 in (25.400 mm), and 26 of the 64 sizes are the default tap drill for at least one standard thread. Inch fractional drills in 1/64 in steps from 1/64 to 1 in.
- Sizes
- 64
- Smallest
- 1/64"
- Largest
- 1"
- Standard
- ANSI/ASME B94.11M
Every Fractional Drill Bit Size, in Inches and Millimetres
64 sizes, ordered smallest to largest. Every row links to that drill's own page, with its equivalents in the other three indexes and the threads it taps.
| Property | Diameter | Property | |
|---|---|---|---|
| Drill | in | mm | Tap drill for |
| 1/64" | 0.0156 | 0.397 | — |
| 1/32" | 0.0313 | 0.794 | — |
| 3/64" | 0.0469 | 1.191 | #0-80 UNF |
| 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" | 0.1563 | 3.969 | — |
| 11/64" | 0.1719 | 4.366 | — |
| 3/16" | 0.1875 | 4.763 | — |
| 13/64" | 0.2031 | 5.159 | — |
| 7/32" | 0.2188 | 5.556 | 1/4"-32 UNEF |
| 15/64" | 0.2344 | 5.953 | — |
| 1/4" | 0.2500 | 6.350 | — |
| 17/64" | 0.2656 | 6.747 | — |
| 9/32" | 0.2813 | 7.144 | 5/16"-32 UNEF |
| 19/64" | 0.2969 | 7.541 | — |
| 5/16" | 0.3125 | 7.938 | 3/8"-16 UNC |
| 21/64" | 0.3281 | 8.334 | — |
| 11/32" | 0.3438 | 8.731 | 3/8"-32 UNEF |
| 23/64" | 0.3594 | 9.128 | — |
| 3/8" | 0.3750 | 9.525 | — |
| 25/64" | 0.3906 | 9.922 | 7/16"-20 UNF |
| 13/32" | 0.4063 | 10.319 | — |
| 27/64" | 0.4219 | 10.716 | 1/2"-13 UNC |
| 7/16" | 0.4375 | 11.113 | — |
| 29/64" | 0.4531 | 11.509 | 1/2"-20 UNF |
| 15/32" | 0.4688 | 11.906 | 1/2"-28 UNEF |
| 31/64" | 0.4844 | 12.303 | 9/16"-12 UNC |
| 1/2" | 0.5000 | 12.700 | — |
| 33/64" | 0.5156 | 13.097 | 9/16"-24 UNEF9/16"-18 UNF |
| 17/32" | 0.5313 | 13.494 | 5/8"-11 UNC |
| 35/64" | 0.5469 | 13.891 | — |
| 9/16" | 0.5625 | 14.287 | — |
| 37/64" | 0.5781 | 14.684 | 5/8"-24 UNEF5/8"-18 UNF |
| 19/32" | 0.5938 | 15.081 | — |
| 39/64" | 0.6094 | 15.478 | — |
| 5/8" | 0.6250 | 15.875 | — |
| 41/64" | 0.6406 | 16.272 | 11/16"-24 UNEF |
| 21/32" | 0.6563 | 16.669 | 3/4"-10 UNC |
| 43/64" | 0.6719 | 17.066 | — |
| 11/16" | 0.6875 | 17.462 | 3/4"-16 UNF |
| 45/64" | 0.7031 | 17.859 | 3/4"-20 UNEF |
| 23/32" | 0.7188 | 18.256 | — |
| 47/64" | 0.7344 | 18.653 | — |
| 3/4" | 0.7500 | 19.050 | — |
| 49/64" | 0.7656 | 19.447 | 13/16"-20 UNEF7/8"-9 UNC |
| 25/32" | 0.7813 | 19.844 | — |
| 51/64" | 0.7969 | 20.241 | — |
| 13/16" | 0.8125 | 20.637 | 7/8"-14 UNF |
| 53/64" | 0.8281 | 21.034 | 7/8"-20 UNEF |
| 27/32" | 0.8438 | 21.431 | — |
| 55/64" | 0.8594 | 21.828 | — |
| 7/8" | 0.8750 | 22.225 | 1"-8 UNC |
| 57/64" | 0.8906 | 22.622 | 15/16"-20 UNEF |
| 29/32" | 0.9063 | 23.019 | — |
| 59/64" | 0.9219 | 23.416 | 1"-12 UNF |
| 15/16" | 0.9375 | 23.813 | — |
| 61/64" | 0.9531 | 24.209 | 1"-20 UNEF |
| 31/32" | 0.9688 | 24.606 | — |
| 63/64" | 0.9844 | 25.003 | 1 1/8"-7 UNC |
| 1" | 1.0000 | 25.400 | 1 1/16"-18 UNEF1 1/8"-18 UNEF1 1/8"-12 UNF+25 |
Diameters are nominal. The tap-drill column shows the threads whose shop-default tap drill is that size; a drill with no entry there is still a standard size, it is simply not the default drill for any thread in this reference.
Sources and Method for the Fractional Drill Bit Chart
- Fractional drill diameterscomputed
Number/letter: bd_warehouse drill_sizes.csv (Apache-2.0) cross-checked against Wikipedia Drill bit sizes (CC BY-SA 4.0). Fractional: computed 1/64 in steps per ANSI B94.11M. Metric: computed BS 328 increment pattern.
Verified against Wikipedia Drill bit sizes (CC BY-SA 4.0); 31/31 checks passed
Computed from the standard's formulas, then checked against published tables.
- Assumptions
- Diameters are nominal. Manufacturing tolerance, wear and run-out all cut oversize.
- Dataset scope: Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.
- Data last verified
- August 1, 2026
How to Cite This Fractional Drill Bit Chart
Citation
ShopMath. "Fractional Drill Sizes — Decimal Inch and Millimetre Chart." ShopMath, verified August 1, 2026, https://shopmath.org/drills/fractional
BibTeX
@misc{shopmath-drills-fractional,
title = {Fractional Drill Sizes — Decimal Inch and Millimetre Chart},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/drills/fractional}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/drills/fractional