What size is a 3/64" drill bit?

A 3/64" drill bit is 0.0469 in in diameter, which is 1.191 mm. It is the 3/64 in fractional size.

What thread does a 3/64" drill bit tap?

A 3/64" drill bit is the tap drill for #0-80 UNF at 75% requested thread engagement, where it leaves 80.8% thread with a cut tap.

What is the metric equivalent of a 3/64" drill bit?

The closest metric drill to a 3/64" drill bit (1.191 mm) is 1.2 mm, which is 1.200 mm — 0.0004 in larger.

Fractional drill · 3/64

3/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes

https://shopmath.org/drills/fractional/3-64 · data verified August 1, 2026

A 3/64" drill bit is 0.0469 in (1.191 mm) in diameter. It is the tap drill for #0-80 UNF at 75% thread engagement with a cut tap, where it leaves 80.8% thread. Diameters are nominal.

Series: Fractional
Designation: 3/64
Inch: 0.0469
mm: 1.191
Standard: ANSI/ASME B94.11M

Fractional Drill · 3/64 · nominal diameter

0.0469 in

Millimetre: 1.191mm
Fraction: 3/64in
Taps: #0-80 UNF

Nominal diameter. As a tap drill it leaves 80.8% thread in #0-80 UNF with a cut tap.

3/64" Drill Bit Size in Inches and Millimetres

The nominal diameter of a 3/64" 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.

3/64" drill bit — decimal inch and millimetre diameter
Property	Value
Diameter, decimal inch	0.0469 in
Diameter, millimetre	1.191 mm
Fraction	3/64 in
Cross-sectional area	0.00173 in²

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

Threads a 3/64" Drill Bit Taps

Every thread in this reference whose tap drill is the 3/64" drill bit, and the thread engagement it leaves. The engagement asked for and the engagement the drill actually produces are different numbers — that gap is why both columns are here.

Threads tapped with a 3/64" drill bit, by thread engagement
Thread	Series	Thread % asked for	Thread % this drill leaves
#0-80 UNF	Unified Fine (UNF)	75%default	80.8
#0-80 UNF	Unified Fine (UNF)	70%	80.8
#0-80 UNF	Unified Fine (UNF)	80%	80.8

Values are for cut taps. Rows marked default are the shop-default engagement for that thread.

3/64" Drill Bit Equivalents in Every Other Drill Series

The closest size to the 3/64" 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 3/64" drill bit
Property	Property	Diameter		Property
Drill	Series	in	mm	Difference, in
#56	Number	0.0465	1.181	−0.0004
A	Letter	0.2340	5.944	+0.1871
1.2 mm	Metric	0.0472	1.200	+0.0004

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 3/64" 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 3/64" drill bit, by diameter
Property	Property	Diameter
Drill	Series	in	mm
1.15 mm	Metric	0.0453	1.150
#56	Number	0.0465	1.181
3/64"	Fractional	0.0469	1.191
1.2 mm	Metric	0.0472	1.200
1.25 mm	Metric	0.0492	1.250

Sources and Method for the 3/64" 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.

Tap drill usagecomputed+compiled

bd_warehouse drill_sizes.csv (Apache-2.0) + Wikipedia Drill bit sizes (CC BY-SA 4.0); fractional and metric computed from ANSI B94.11M / BS 328 increment patterns

Verified against drills: 31 checks passed across 1 harness(es)

Part computed from the standard's formulas, part compiled from agreeing public sources.

Formula

Fractional drill diameter

Ø  =  3/64 in  =  0.0469 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.
Tap drill usage assumes cut taps. #0-80 UNF at 75% requested engagement is what this drill is normally bought for.
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 3/64" Drill Bit Reference

Citation

ShopMath. "3/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/fractional/3-64

BibTeX

@misc{shopmath-drills-fractional-3-64,
  title        = {3/64" Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/drills/fractional/3-64}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/drills/fractional/3-64

Common Questions About the 3/64" Drill Bit

What size is a 3/64" drill bit?: A 3/64" drill bit is 0.0469 in in diameter, which is 1.191 mm. It is the 3/64 in fractional size.
What thread does a 3/64" drill bit tap?: A 3/64" drill bit is the tap drill for #0-80 UNF at 75% requested thread engagement, where it leaves 80.8% thread with a cut tap.
What is the metric equivalent of a 3/64" drill bit?: The closest metric drill to a 3/64" drill bit (1.191 mm) is 1.2 mm, which is 1.200 mm — 0.0004 in larger.

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