Metric drill · 12 mm
12 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes
https://shopmath.org/drills/metric/12mm · data verified August 1, 2026
A 12 mm drill bit is 0.4724 in (12.000 mm) in diameter. The nearest fractional size is 15/32" at 0.4688 in. Diameters are nominal.
- Series
- Metric
- Designation
- 12 mm
- Inch
- 0.4724
- mm
- 12.000
- Standard
- ANSI/ASME B94.11M
Metric Drill · 12 mm · nominal diameter
0.4724 in
- Millimetre
- 12.000mm
Nominal diameter. A worn or run-out drill cuts oversize, which leaves less thread in a tapped hole than the table says.
12 mm Drill Bit Size in Inches and Millimetres
The nominal diameter of a 12 mm drill bit. Drill sizes are nominal — a worn drill, run-out or a soft material that closes in behind the cut all move the finished hole.
| Property | Value |
|---|---|
| Diameter, decimal inch | 0.4724 in |
| Diameter, millimetre | 12.000 mm |
| Cross-sectional area | 0.17530 in² |
1 in = 25.4 mm exactly, so the two columns are the same value in different units, not two measurements.
12 mm Drill Bit Equivalents in Every Other Drill Series
The closest size to the 12 mm drill bit in each of the other three indexes, with the difference in inches. None of them is the same drill — check the difference before substituting one into a tapped hole.
| Property | Property | Diameter | Property | |
|---|---|---|---|---|
| Drill | Series | in | mm | Difference, in |
| #1 | Number | 0.2280 | 5.791 | −0.2444 |
| Z | Letter | 0.4130 | 10.490 | −0.0594 |
| 15/32" | Fractional | 0.4688 | 11.906 | −0.0037 |
A positive difference means the equivalent drill is larger, which leaves less thread in a tapped hole. Sizes without a link are stored for the nearest-drill calculation but do not carry their own page.
Drill Sizes Either Side of the 12 mm Drill Bit
Ordered by diameter across all four indexes, so the next size up may be a letter, a fraction or a metric drill rather than the next one in this series.
Sources and Method for the 12 mm Drill Bit Size
- Drill diametercomputed
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. Drill manufacturing tolerance, wear and run-out all cut oversize, and every one of those moves a tapped hole toward less thread than the table says.
- 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 12 mm Drill Bit Reference
Citation
ShopMath. "12 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/metric/12mm
BibTeX
@misc{shopmath-drills-metric-12mm,
title = {12 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
author = {{ShopMath}},
year = {2026},
howpublished = {\url{https://shopmath.org/drills/metric/12mm}},
note = {Data verified 2026-08-01}
}Permanent URL
https://shopmath.org/drills/metric/12mm
Common Questions About the 12 mm Drill Bit
What size is a 12 mm drill bit?
- A 12 mm drill bit is 0.4724 in in diameter, which is 12.000 mm.
What fraction is a 12 mm drill bit closest to?
- A 12 mm drill bit (0.4724 in) sits closest to the 15/32" fractional drill at 0.4688 in, a difference of 0.0037 in.
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