What size is a 5.5 mm drill bit?

A 5.5 mm drill bit is 0.2165 in in diameter, which is 5.500 mm.

What fraction is a 5.5 mm drill bit closest to?

A 5.5 mm drill bit (0.2165 in) sits closest to the 7/32" fractional drill at 0.2188 in, a difference of 0.0022 in.

What bolt fits through a 5.5 mm drill bit hole?

A hole drilled with a 5.5 mm drill bit is the standard normal clearance hole for M5×0.5, and a clearance hole for 1 other fastener sizes listed on this page.

Metric drill · 5.5 mm

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

https://shopmath.org/drills/metric/5-5mm · data verified August 1, 2026

A 5.5 mm drill bit is 0.2165 in (5.500 mm) in diameter. The nearest fractional size is 7/32" at 0.2188 in. Diameters are nominal.

Series: Metric
Designation: 5.5 mm
Inch: 0.2165
mm: 5.500
Standard: ANSI/ASME B94.11M

Metric Drill · 5.5 mm · nominal diameter

0.2165 in

Millimetre: 5.500mm

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

5.5 mm Drill Bit Size in Inches and Millimetres

The nominal diameter of a 5.5 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.

5.5 mm drill bit — decimal inch and millimetre diameter
Property	Value
Diameter, decimal inch	0.2165 in
Diameter, millimetre	5.500 mm
Cross-sectional area	0.03683 in²

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

Threads a 5.5 mm Drill Bit Taps

Every thread in this reference whose tap drill is the 5.5 mm 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 5.5 mm drill bit, by thread engagement
Thread	Series	Thread % asked for	Thread % this drill leaves
M6×0.75	ISO Metric Fine	50%	51.3

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

Fasteners That Pass Through a 5.5 mm Drill Bit Hole

A hole drilled with a 5.5 mm 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 5.5 mm drill bit
Fastener	Series	Clearance class
M5×0.5	ISO Metric Fine	normal
M5×0.8	ISO Metric Coarse	normal

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.

5.5 mm Drill Bit Equivalents in Every Other Drill Series

The closest size to the 5.5 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 5.5 mm drill bit
Property	Property	Diameter		Property
Drill	Series	in	mm	Difference, in
#3	Number	0.2130	5.410	−0.0035
A	Letter	0.2340	5.944	+0.0175
7/32"	Fractional	0.2188	5.556	+0.0022

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 5.5 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 5.5 mm drill bit, by diameter
Property	Property	Diameter
Drill	Series	in	mm
5.4 mm	Metric	0.2126	5.400
#3	Number	0.2130	5.410
5.5 mm	Metric	0.2165	5.500
7/32"	Fractional	0.2188	5.556
5.6 mm	Metric	0.2205	5.600

Sources and Method for the 5.5 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.

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.

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 5.5 mm Drill Bit Reference

Citation

ShopMath. "5.5 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes." ShopMath, verified August 1, 2026, https://shopmath.org/drills/metric/5-5mm

BibTeX

@misc{shopmath-drills-metric-5-5mm,
  title        = {5.5 mm Drill Bit Size — Decimal Inch, Millimetre and Tap Sizes},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/drills/metric/5-5mm}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/drills/metric/5-5mm

Common Questions About the 5.5 mm Drill Bit

What size is a 5.5 mm drill bit?: A 5.5 mm drill bit is 0.2165 in in diameter, which is 5.500 mm.
What fraction is a 5.5 mm drill bit closest to?: A 5.5 mm drill bit (0.2165 in) sits closest to the 7/32" fractional drill at 0.2188 in, a difference of 0.0022 in.
What bolt fits through a 5.5 mm drill bit hole?: A hole drilled with a 5.5 mm drill bit is the standard normal clearance hole for M5×0.5, and a clearance hole for 1 other fastener sizes listed on this page.

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