Drill Bit Size Chart for #36, #44, Number, Letter & Fractional Bits

Find the decimal and metric size for #30, #29, #36, #44, #11, fractional, letter, and wire gauge drill bits before drilling, tapping, or choosing a pilot hole. If you search for “size 44 drill bit” or “drill bit 44 size,” the standard #44 wire gauge drill is 0.0860 in, about 2.184 mm.

Direct answers

#30, #29 and #44 Drill Bit Size Quick Answers

Use these values when you need the exact numbered drill diameter before tapping, checking a pilot hole, or comparing a metric substitute.

#30 drill bit size

A #30 drill bit is 0.1285 inches in diameter, about 3.264 mm. It is slightly larger than 1/8 in (0.1250 in), so do not treat 1/8 in as the same size when a drawing, tap chart, or clearance spec calls for #30.

Use the exact numbered bit when the hole size is tied to a tap, close clearance, or tolerance-sensitive layout.

#29 drill bit size

A #29 drill bit is 0.1360 inches in diameter, about 3.454 mm. It is commonly listed as an 8-32 UNC tap-drill size, but the correct choice still depends on thread form, material, and the tap chart you are using.

For tapping, check the tap chart or manufacturer data before drilling final holes.

#44 drill bit size

A #44 drill bit is 0.0860 inches in diameter, about 2.184 mm. The same answer applies to searches such as “size 44 drill bit” and “drill bit 44 size.”

A 2.2 mm bit is slightly larger; use #44 when pilot-hole precision or thread fit matters.

Quick Answers for Common Drill Bit Sizes and Tap Drills

Use these quick answers when you need a drill diameter, a common tap-drill reference, or a nearby size comparison before you drill. For tapped holes, always confirm the tap chart, material, and required thread percentage before drilling final holes.

What you need	Size or common reference	Use this note
#44 drill bit	#44 = 0.0860 in / 2.184 mm	A 2.2 mm bit is nearby but slightly larger. Use an actual #44 bit when the hole size, fit, or thread preparation matters.
#30 drill bit compared with 1/8 in	#30 = 0.1285 in; 1/8 in = 0.1250 in	#30 is slightly larger than 1/8 in. Do not round down when a drawing, tap chart, clearance chart, or procedure calls for #30.
6-32 UNC tap drill	Common reference: #36 / 0.1065 in	Use this as a common starting reference, then confirm the tap chart, material, and required thread percentage.
8-32 UNC tap drill	Common reference: #29 / 0.1360 in	Verify the tap chart before final drilling, especially when material, thread fit, or thread percentage is important.
1/4-20 UNC tap drill	Common reference: #7 / 0.2010 in	#7 is a common 1/4-20 UNC tap-drill reference. Verify the chart, material, and thread percentage before drilling final holes.
Letter F drill bit	Letter F = 0.2570 in / 6.528 mm	Letter F is also a common 5/16-18 UNC tap-drill reference. Confirm the thread chart before tapping.
M6 x 1.0 tap drill	Common reference: 5.0 mm / 0.1969 in	Use the metric tap chart for the thread standard and material. Do not substitute a nearby numbered or fractional bit without checking the required fit.

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Common number drill bit sizes

Use these common number drill sizes as lookup references, then compare the chart’s decimal inch and millimeter columns before choosing a nearby bit.

Number drill bit	Decimal inches	Metric diameter	Use note
#44 drill bit	0.0860 in	2.184 mm	Small numbered bit for precision pilot holes. A 2.2 mm bit is nearby but slightly larger, so use #44 when the exact hole size matters.
#36 drill bit size	0.1065 in	2.705 mm	Commonly checked for tap-drill and clearance lookups.
#30 drill size	0.1285 in	3.264 mm	Often compared with 1/8 in, but it is slightly larger.
#29 drill bit size	0.1360 in	3.454 mm	Commonly referenced in tap-drill lookups.
#25 drill bit	0.1495 in	3.797 mm	Common 10-24 UNC tap-drill reference. Confirm the tap chart, material, and required thread percentage before drilling final holes.
#21 drill bit	0.1590 in	4.039 mm	Numbered size near 5/32 in. Use #21 when the chart, drawing, or procedure calls for this exact diameter.
#11 drill bit size	0.1910 in	4.851 mm	Compare nearby fractional and metric sizes before substituting.
#7 drill bit	0.2010 in	5.105 mm	Common 1/4-20 UNC tap-drill reference. Verify the tap chart, material, and required thread percentage before tapping.

These values are lookup references, not universal instructions. Check the chart data, thread requirement, material context, and the source you are working from before final drilling.

Closest Common Drill Bit Substitutes

Use these nearby sizes as comparison checks only. A close metric or fractional bit may be acceptable for rough pilot holes, but use the specified size for tapping, close-clearance holes, drawings, or any fit that depends on the exact diameter.

Specified bit	Exact decimal	Exact metric	Nearby common size	Use the exact size when
#44	0.0860 in	2.184 mm	2.2 mm — slightly larger	The pilot hole size, thread fit, or drawing calls for #44.
#36	0.1065 in	2.705 mm	2.7 mm — very close, slightly smaller	You are tapping 6-32 threads, checking close clearance, or following a chart that specifies #36.
#30	0.1285 in	3.264 mm	1/8 in — close but smaller	A drawing, tap chart, clearance chart, or procedure specifies #30.
#29	0.1360 in	3.454 mm	3.5 mm — slightly larger	You are tapping 8-32 threads, checking close clearance, or following a chart that specifies #29.
#25	0.1495 in	3.797 mm	3.8 mm — very close, slightly larger	You are tapping 10-24 threads, checking close clearance, or following a chart that specifies #25.
#21	0.1590 in	4.039 mm	4.0 mm — slightly smaller	A chart, drawing, or procedure specifies #21.
#11	0.1910 in	4.851 mm	4.8 mm — slightly smaller	A chart, drawing, or procedure specifies #11.
#7	0.2010 in	5.105 mm	5.1 mm — very close, slightly smaller	You are tapping 1/4-20 threads or following a chart that specifies #7.

Choose the right lookup path

How to use these answers: first read the exact numbered drill size, then decide what job the hole is doing. A tap hole, a loose clearance hole, and a wood pilot hole can call for different choices even when the nearest fraction or metric size looks close.

If a drawing, tap chart, or manufacturer spec gives a numbered drill size, start with that exact numbered bit. For loose clearance or rough layout, a nearby fractional or metric bit may be acceptable, but check the spec before drilling final holes.

Tap drill

Start with the thread size, then read the recommended drill size. Do not round to the nearest fraction until you understand the thread requirement.

Pilot hole

Start with the screw material and pilot-hole purpose. A pilot hole is not the same decision as a tap-drill size.

Closest substitute

Use substitutes only as a reference check. Compare decimal inches and millimeters before choosing a nearby bit.

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Drill Bit Size Conversion Chart

Systems: Number, Fraction, Decimal, MM • Range 1/16 → 1/2 • A4

Number	Fraction	Decimal (in)	Millimeters
	1/16"	0.0625	1.59
#52		0.0635	1.61
#51		0.0670	1.70
#50		0.0700	1.78
#49		0.0730	1.85
#48		0.0760	1.93
	5/64"	0.0781	1.98
#47		0.0785	1.99
		0.0787	2.00
#46		0.0810	2.06
#45		0.0820	2.08
#44		0.0860	2.18
#43		0.0890	2.26
#42		0.0935	2.38
	3/32"	0.0938	2.38
#41		0.0960	2.44
#40		0.0980	2.49
		0.0984	2.50
#39		0.0995	2.53
#38		0.1015	2.58
#37		0.1040	2.64
#36		0.1065	2.71
	7/64"	0.1094	2.78
#35		0.1100	2.79
#34		0.1110	2.82
#33		0.1130	2.87
#32		0.1160	2.95
		0.1181	3.00
#31		0.1200	3.05
	1/8"	0.1250	3.17
#30		0.1285	3.26
#29		0.1360	3.45
		0.1378	3.50
#28		0.1405	3.57
	9/64"	0.1406	3.57
#27		0.1440	3.66
#26		0.1470	3.73
#25		0.1495	3.80
#24		0.1520	3.86
#23		0.1540	3.91
	5/32"	0.1563	3.97
#22		0.1570	3.99
		0.1575	4.00
#21		0.1590	4.04
#20		0.1610	4.09
#19		0.1660	4.22
#18		0.1695	4.30
	11/64"	0.1719	4.37
#17		0.1730	4.39
#16		0.1770	4.50
		0.1772	4.50
#15		0.1800	4.57
#14		0.1820	4.62
#13		0.1850	4.70
	3/16"	0.1875	4.76
#12		0.1890	4.80
#11		0.1910	4.85
#10		0.1935	4.92
#9		0.1960	4.98
		0.1969	5.00
#8		0.1990	5.05
#7		0.2010	5.11
	13/64"	0.2031	5.16
#6		0.2040	5.18
#5		0.2055	5.22
#4		0.2090	5.31
#3		0.2130	5.41
		0.2165	5.50
	7/32"	0.2188	5.56
#2		0.2210	5.61
#1		0.2280	5.79
		0.2340	5.94
	15/64"	0.2344	5.95
		0.2362	6.00
		0.2380	6.04
		0.2420	6.15
		0.2460	6.25
	1/4"	0.2500	6.35
		0.2559	6.50
		0.2570	6.53
		0.2610	6.63
	17/64"	0.2656	6.75
		0.2660	6.76
		0.2720	6.91
		0.2756	7.00
		0.2770	7.04
		0.2810	7.14
	9/32"	0.2813	7.14
		0.2900	7.37
		0.2950	7.49
		0.2953	7.50
	19/64"	0.2969	7.54
		0.3020	7.67
	5/16"	0.3125	7.94
		0.3150	8.00
		0.3160	8.03
		0.3230	8.20
	21/64"	0.3281	8.33
		0.3320	8.43
		0.3346	8.50
		0.3390	8.61
	11/32"	0.3438	8.73
		0.3480	8.84
		0.3543	9.00
		0.3580	9.09
	23/64"	0.3594	9.13
		0.3680	9.35
		0.3740	9.50
	3/8"	0.3750	9.53
		0.3770	9.58
		0.3860	9.80
	25/64"	0.3906	9.92
		0.3937	10.00
		0.3970	10.08
		0.4040	10.26
	13/32"	0.4063	10.32
		0.4130	10.49
		0.4134	10.50
	27/64"	0.4219	10.72
		0.4331	11.00
	7/16"	0.4375	11.11
		0.4528	11.50
	29/64"	0.4531	11.51
	15/32"	0.4688	11.91
		0.4724	12.00
	31/64"	0.4844	12.30
		0.4921	12.50
	1/2"	0.5000	12.70

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Understanding Drill Bit Sizing Systems

Drill bits in the US are categorized into three systems, each designed for specific manufacturing or construction precision:

Fractional Sizes: From 1/64" to 1" (and up). These are the "general-purpose" bits used in most home shops for wood and basic metal projects.
Wire Gauge (Number) Sizes: Designed for precision metalworking. Ranges from #1 (0.2280") down to #80 (0.0135"). These are essential for tapping machine threads accurately—using the wrong bit here often ruins the thread or breaks the tap.
Letter Sizes: Designed to bridge the gaps between fractional sizes, ranging from A (0.2340") to Z (0.4130"). Machinists use these for creating tight clearance holes for bolts.

Selecting the Right Bit for Your Project

General Construction: When working with wood or standard light metal, fractional bits provide the most common and accessible sizing increments.
Machining & Tapping: Numbered wire gauge bits are non-negotiable for precision threading. Always verify the tap drill chart; for example, a #36 drill bit is the industry standard for 6-32 threads.
Precision Clearances: If you need a bolt to slide through a hole perfectly without "slop," letter-sized drill bits offer the precision tolerances fractional bits lack.

Wood Screw Pilot Hole Guide

Prevent split wood and stripped screws. Match your drill bit to the screw size and wood hardness.

Screw Size	Softwood Pilot (Pine, Cedar)	Hardwood Pilot (Oak, Maple)	Clearance Hole (Shank pass-through)
#4	1/16"	5/64"	1/8"
#6	1/16"	5/64"	9/64"
#8	5/64"	3/32"	11/64"
#10	3/32"	7/64"	3/16"
#12	7/64"	1/8"	7/32"
#14	9/64"	11/64"	1/4"

Which Drill Bit Type?

Expert guidance on selecting bit geometry and materials for professional results.

Twist Bit

Wood, Metal, Plastic

General purpose bits. Standard 118° is for soft materials; 135° split-point is for harder metals.

Brad Point

Wood Only

Precision center point prevents wandering. Ideal for clean holes in cabinetry.

Masonry Bit

Brick, Concrete

Carbide-tipped for masonry. Usually paired with a hammer drill for masonry work.

Cobalt (M35/M42)

Hard Metals

Resistant to high heat. Often used for stainless steel and professional machining.

Professional Drilling Tips

How to use this chart to improve your accuracy in the workshop.

Measure Diameter

If markings are worn, use a digital caliper to measure the drill shank. Cross-reference this with our Decimal column.

Prevent Bit Walking

In metal, use a Center Punch to create a dimple. In wood, use a Brad Point bit to ensure the hole starts exactly where intended.

Calculate Clearance

Always use a Clearance Hole for the screw shank so the threads only engage the second piece of material for a tight joint.

Common Uses for Specific Drill Bit Sizes

Selecting the right drill bit is essential for a clean and secure hole.

General Construction (Fractional)

Common sizes like 1/8", 1/4", and 3/8" are standard for drilling into wood, drywall, and plastic.

Threading and Tapping (Number/Wire Gauge)

Numbered drill bits are essential when creating threads in metal. Using the exact size prevents tap breakage and ensures strong threads. For example, using a #36 drill bit is critical before tapping a 6-32 thread. Planning to tap a hole? Reference our complete Bolt & Screw Sizes Chart to find the perfect drill bit for any thread.

Clearance Holes (Letter)

When a bolt needs to pass through a material without threading into it, letter-sized drill bits often provide the perfect clearance gap that fractional bits might miss. For general wood screws, ensure a tight fit by checking our Screw Size Reference. Need to convert measurements? Use our Fraction to Decimal Chart.

Tap Drill Selection Guide

Matching the correct drill bit to your tap ensures strong threads and prevents broken tools.

For machine screws, the drill bit is not just a clearance hole. It controls thread engagement. For example, a #36 drill bit is the common tap drill for 6-32 UNC, #29 is common for 8-32 UNC, and #7 is common for 1/4-20 UNC. Always verify material and thread percentage before tapping metal.

Thread Size	Threads / Inch	Tap Drill	Decimal (in)
6-32 UNC	32	#36	0.1065"
8-32 UNC	32	#29	0.1360"
10-24 UNC	24	#25	0.1495"
1/4"-20 UNC	20	#7	0.2010"
5/16"-18 UNC	18	Letter F	0.2570"
M6 x 1.0	1.0mm	5.0mm	0.1969"

Related workshop charts for drilling and fasteners

After checking a drill size, the next reference is often the fastener, the wrench, or the decimal equivalent. Use Screw Size for screw diameter context, Bolt Size for thread and wrench checks, and Fraction to Decimal when a drawing uses fractional inches.

Screw SizesWorkshop

Size	Pilot	Clear
#4	1/16"	9/64"
#6	5/64"	11/64"
#8	3/32"	13/64"
#10	7/64"	1/4"
#12	1/8"	17/64"
1/4"	-	F
5/16"	-	P
3/8"	-	W
M4	2.5mm	4.5mm
M6	3.5mm	6.6mm

Screw Size Chart

Identify screw sizes, thread pitches, and head types for woodworking and repairs.

Special Workshop EngineeringHomehardware woodworking

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Bolt SizesWorkshop

Size	Pitch/TPI	Head
M3	0.5	5.5
M4	0.7	7.0
M5	0.8	8.0
M6	1.0	10.0
M8	1.25	13.0
1/4"	20	7/16"
5/16"	18	1/2"
3/8"	16	9/16"

Bolt & Screw Sizes

Metric and imperial bolt, screw, and thread pitch reference.

Special WorkshopAutomotiveEngineering hardware automotive

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Fraction → DecimalEducational

Fraction	Decimal	Percent
1/64	0.0156	1.56%
1/32	0.0313	3.13%
1/16	0.0625	6.25%
1/8	0.1250	12.5%
3/16	0.1875	18.8%
1/4	0.2500	25%
5/16	0.3125	31.3%
3/8	0.3750	37.5%
1/2	0.5000	50%
3/4	0.7500	75%

Fraction to Decimal

Fractions from 1/64 to whole numbers for math education and precision cutting.

Special Education Workshop Engineering education math woodworking engineering

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Wrench SizesWorkshop

Size	M-Bolt	S-Bolt
8mm	M5	5/16"
10mm	M6	-
7/16"	-	1/4"
13mm	M8	-
1/2"	-	5/16"
17mm	M10	-
9/16"	-	3/8"
19mm	M12	3/4"
3/4"	-	1/2"

Wrench Size Chart

Wrench sizes for common bolt heads with metric and imperial references.

Special Workshop Engineering hardware automotive

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Frequently Asked Questions

What size is a #30 drill bit?

A #30 drill bit is 0.1285 inches in diameter, about 3.264 mm. It is close to 1/8 in but slightly larger, so use a #30 bit when a tap chart, clearance chart, drawing, or procedure calls for #30.

What size is a #29 drill bit?

A #29 drill bit is 0.1360 inches in diameter, about 3.454 mm. It is commonly listed as an 8-32 UNC tap-drill size, but the correct drill depends on thread standard, material, and the tap chart you are following.

What size is a #36 drill bit?

A #36 drill bit is 0.1065 inches, or about 2.705 mm.

What size is a #44 drill bit?

A #44 drill bit is 0.0860 inches in diameter, about 2.184 mm. The same size is often searched as “size 44 drill bit” or “drill bit 44 size.” A nearby 2.2 mm bit is slightly larger, not an exact substitute.

What is the closest substitute for a #36 drill bit?

A 2.7 mm bit is very close to a #36 drill bit, but use an actual #36 bit when tapping 6-32 threads or when the fit matters.

What is the closest substitute for a #44 drill bit?

A 2.2 mm bit is the closest common metric check for a #44 drill bit, but it is slightly larger. Use #44 when thread fit or pilot-hole precision matters.

What size is a #11 drill bit?

A #11 drill bit is 0.1910 inches, or about 4.851 mm.

What size is a #21 drill bit?

A #21 drill bit is 0.1590 inches in diameter, which converts to 4.039 mm.

What is the actual diameter of a #1 wire gauge drill bit?

A #1 wire gauge drill bit has a decimal diameter of 0.2280 inches. In the number system, #1 is the largest, and #80 is the smallest (0.0135 inches).

What is the equivalent of a Letter F drill bit?

A Letter F drill bit has a decimal diameter of 0.2570 inches. It is most commonly used as the tap drill for a 5/16"-18 UNC thread.

What is the difference between 118° and 135° drill bits?

118-degree bits are general-purpose and ideal for wood and soft metals. 135-degree split-point bits are designed for harder metals like stainless steel because they bite into the material and do not walk across the surface.

Which drill bit should I use for a 1/4"-20 tap?

The standard tap drill for a 1/4"-20 UNC thread is a #7 drill bit (0.2010 inches). This ensures approximately 75% thread engagement.

How do I convert millimeters to drill bit sizes?

Use the chart to compare the metric measurement with the nearest number, letter, or fractional drill bit. For example, a 6 mm bit is slightly smaller than a 1/4 inch (6.35 mm) bit.

What is a wire gauge drill bit?

Wire gauge sizes are a numbered system from #1 to #80 typically used for small-diameter precision drilling in machining, tapping, electronics, and model work.

How do I choose between fractional and wire drill bits?

Choose fractional bits for general carpentry or clearance holes where loose tolerance is acceptable. Choose wire gauge bits for precision tasks like tapping metal, where exact diameter is required to ensure thread strength.

What is the smallest wire gauge drill bit?

The #80 drill bit is the smallest in the wire gauge system, measuring 0.0135 inches (0.343 mm).

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