What size is a 9/64" drill bit?

A 9/64" drill bit is 0.1406 in in diameter, which is 3.572 mm. It is the 9/64 in fractional size.

What is the metric equivalent of a 9/64" drill bit?

The closest metric drill to a 9/64" drill bit (3.572 mm) is 3.6 mm, which is 3.600 mm — 0.0011 in larger.

What bolt fits through a 9/64" drill bit hole?

A hole drilled with a 9/64" drill bit is the standard close clearance hole for #5-44 UNF, and a clearance hole for 1 other fastener sizes listed on this page.

Fractional drill · 9/64

9/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes

https://shopmath.org/drills/fractional/9-64 · data verified August 1, 2026

A 9/64" drill bit is 0.1406 in (3.572 mm) in diameter. Diameters are nominal.

Series: Fractional
Designation: 9/64
Inch: 0.1406
mm: 3.572
Standard: ANSI/ASME B94.11M

Fractional Drill · 9/64 · nominal diameter

0.1406 in

Millimetre: 3.572mm
Fraction: 9/64in

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

9/64" Drill Bit Size in Inches and Millimetres

The nominal diameter of a 9/64" 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.

9/64" drill bit — decimal inch and millimetre diameter
Property	Value
Diameter, decimal inch	0.1406 in
Diameter, millimetre	3.572 mm
Fraction	9/64 in
Cross-sectional area	0.01553 in²

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

Fasteners That Pass Through a 9/64" Drill Bit Hole

A hole drilled with a 9/64" drill bit is the standard clearance hole for these fasteners — the through-hole the bolt passes freely, not the tapped hole.

Fasteners whose clearance hole is drilled with a 9/64" drill bit
Fastener	Series	Clearance class
#5-44 UNF	Unified Fine (UNF)	close
#5-40 UNC	Unified Coarse (UNC)	close

Clearance classes per ISO 273 (metric) and ASME B18.2.8 (inch): close for located joints, normal for general assembly, loose for slotted or adjustable joints.

9/64" Drill Bit Equivalents in Every Other Drill Series

The closest size to the 9/64" 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 9/64" drill bit
Property	Property	Diameter		Property
Drill	Series	in	mm	Difference, in
#28	Number	0.1405	3.569	−0.0001
A	Letter	0.2340	5.944	+0.0934
3.6 mm	Metric	0.1417	3.600	+0.0011

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 9/64" 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 9/64" drill bit, by diameter
Property	Property	Diameter
Drill	Series	in	mm
3.5 mm	Metric	0.1378	3.500
#28	Number	0.1405	3.569
9/64"	Fractional	0.1406	3.572
3.6 mm	Metric	0.1417	3.600
#27	Number	0.1440	3.658

Sources and Method for the 9/64" 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.

Formula

Fractional drill diameter

Ø  =  9/64 in  =  0.1406 in

Fractional drills are exact fractions of an inch in 1/64 in steps; the decimal is the fraction evaluated, not a measurement.

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 9/64" Drill Bit Reference

Citation

ShopMath. "9/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/fractional/9-64

BibTeX

@misc{shopmath-drills-fractional-9-64,
  title        = {9/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/drills/fractional/9-64}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/drills/fractional/9-64

Common Questions About the 9/64" Drill Bit

What size is a 9/64" drill bit?: A 9/64" drill bit is 0.1406 in in diameter, which is 3.572 mm. It is the 9/64 in fractional size.
What is the metric equivalent of a 9/64" drill bit?: The closest metric drill to a 9/64" drill bit (3.572 mm) is 3.6 mm, which is 3.600 mm — 0.0011 in larger.
What bolt fits through a 9/64" drill bit hole?: A hole drilled with a 9/64" drill bit is the standard close clearance hole for #5-44 UNF, and a clearance hole for 1 other fastener sizes listed on this page.

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