What size is a 1 mm drill bit?

A 1 mm drill bit is 0.0394 in in diameter, which is 1.000 mm.

What fraction is a 1 mm drill bit closest to?

A 1 mm drill bit (0.0394 in) sits closest to the 3/64" fractional drill at 0.0469 in, a difference of 0.0075 in.

Metric drill · 1 mm

1 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes

https://shopmath.org/drills/metric/1mm · data verified August 1, 2026

A 1 mm drill bit is 0.0394 in (1.000 mm) in diameter. The nearest fractional size is 3/64" at 0.0469 in. Diameters are nominal.

Series: Metric
Designation: 1 mm
Inch: 0.0394
mm: 1.000
Standard: ANSI/ASME B94.11M

Metric Drill · 1 mm · nominal diameter

0.0394 in

Millimetre: 1.000mm

Nominal diameter. A worn or run-out drill cuts oversize, which leaves less thread in a tapped hole than the table says.

1 mm Drill Bit Size in Inches and Millimetres

The nominal diameter of a 1 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.

1 mm drill bit — decimal inch and millimetre diameter
Property	Value
Diameter, decimal inch	0.0394 in
Diameter, millimetre	1.000 mm
Cross-sectional area	0.00122 in²

1 in = 25.4 mm exactly, so the two columns are the same value in different units, not two measurements.

1 mm Drill Bit Equivalents in Every Other Drill Series

The closest size to the 1 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.

Nearest number, letter, fractional and metric equivalents to a 1 mm drill bit
Property	Property	Diameter		Property
Drill	Series	in	mm	Difference, in
#61	Number	0.0390	0.991	−0.0004
A	Letter	0.2340	5.944	+0.1946
3/64"	Fractional	0.0469	1.191	+0.0075

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 1 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.

Standard drill sizes adjacent to a 1 mm drill bit, by diameter
Property	Property	Diameter
Drill	Series	in	mm
0.95 mm	Metric	0.0374	0.950
0.98 mm	Metric	0.0386	0.980
1 mm	Metric	0.0394	1.000
#60	Number	0.0400	1.016
#59	Number	0.0410	1.041

Sources and Method for the 1 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 this data is built and checked →

How to Cite This 1 mm Drill Bit Reference

Citation

ShopMath. "1 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/metric/1mm

BibTeX

@misc{shopmath-drills-metric-1mm,
  title        = {1 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/drills/metric/1mm}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/drills/metric/1mm

Common Questions About the 1 mm Drill Bit

What size is a 1 mm drill bit?: A 1 mm drill bit is 0.0394 in in diameter, which is 1.000 mm.
What fraction is a 1 mm drill bit closest to?: A 1 mm drill bit (0.0394 in) sits closest to the 3/64" fractional drill at 0.0469 in, a difference of 0.0075 in.

All metric drill sizes · Complete drill size chart · Every drill series