Size Chart for Bolts and Different Types
This post was last updated on April 7th, 2023 at 09:10 am
Bolts are a type of externally threaded fastener. During assembly, it won’t rotate, but the nut is turned to tighten it. The screw is often placed into an already-existing threaded hole or is passed through the material to create its own internal thread. It is then torqued to tighten the screw (skip straight to the size chart for bolts).
Let’s get started!
Jump right into the Frequently Asked Questions
Size Chart for Bolts Table of Content
- Types of bolts
- Size Chart for Bolts
- Metric clearance and tapping drill hole sizes chart
- How to choose the size of the right bolt and what is the best size for you
- Frequently Asked Questions
Types of bolts
- Elevator bolt; Similar to the carriage bolt but elevator bolt with a thin flat or countersunk head and a square undercut, used in conveyor system setups.
- Hex bolt: Heavy Hex bolt is designed with a hexagonal head or hex head bolts that are to be driven by a wrench and external machine threads.
- Lag bolt: Lag bolts, also known as lag screws, are one of the toughest fasteners and are extremely sturdy. This kind of bolt can create its thread and form a friction joint in wood with its coarse threads and other soft materials when tightened.
- J-bolt: J-bolts are fasteners in the shape of a J with threads in the non-curved area and a hook for support in another section. J-bolts are used in construction and available in various lengths and diameters.
- U-bolt: A U-bolt has threads on both sides and is shaped like the letter “U,”. The size of the pipe that a U-bolt is clamping might define it. The most durable and non-corrosive metals, such as 316 stainless steel, 304 stainless steel, and plain carbon steel, are used to make U-bolts.
- Hanger bolt: When used to suspend items. hanger bolts or headless bolts with threads on both ends add an external thread or form a concealed fastening joint.
Other types of bolts include flange bolts, flat head bolts, sex bolt also known as barrel bolt or connector bolt, square bolts, shoulder bolt, carriage bolt also called coach bolt, eye bolts, and anchor bolt.
Size Chart for Bolts
Let us now see some bolt size charts. We will see both imperial and metric charts for bolt dimensions and the thread pitch.
Size Chart for Bolts (Imperial)
|Threads||Shark diameter||Width across flats||Head thickness|
|Nominal bolt size||UNC||UNF||Max||Min||Max||Min||Max||Min|
|1/4 mm 0.00985inches||20 mm 0.788inches||28 mm 1.1inches||0.25 mm 0.0099inches||0.246 mm 0.0097inches||0.438mm 0.0172inches||0.428 mm 0.0169inches||0.163 mm 0.0458inches||0.15 mm 0.045inches|
|5/16 mm 0.012 inches||18 mm 0.71 inches||24 mm 0.95inches||0.3125mm 0.0123inches||0.3066 mm 0.012inches||0.5 mm 0.0197inches||0.489 mm 0.0192inches||0.211 mm 0.00477inches||0.195 mm 0.00768inches|
|3/8 mm 0.015 inches||16 mm 0.63 inches||24 mm 0.95 inches||0.375 mm 0.0147inches||0.369 mm 0.0146inches||0.562 mm 0.0221inches||0.551 mm 0.0219inches||0.243 mm 0.0957 inches||0.226 mm 0.089 inches|
|7/16 mm 0.017inches||14 mm 0.55 inches||20 mm 0.788inches||0.4375 mm 0.0172inches||0.4306 mm 0.0168inches||0.625 mm 0.0246inches||0.612 mm 0.0243inches||0.291 mm 0.0114 inches||0.272 mm 0.0107 inches|
|1/2 mm 0.016inches||13 mm 0.51 inches||20 mm 0.788inches||0.5 mm 0.0197inches||0.493 mm 0.0194inches||0.75 mm 0.0296inches||0.736 mm 0.029 inches||0.323 mm 0.0127 inches||0.302 mm 0.0119 inches|
|5/8 mm 0.025inches||11 mm 0.43 inches||18 mm 0.709inches||0.625 mm 0.0246inches||0.617 mm 0.0243inches||0.938 mm 0.0369inches||0.922 mm 0.0362inches||0.403 mm 0.0158 inches||0.378mm 0.0149 inches|
|3/4 mm 0.03 inches||10 mm 0.394inches||16mm 0.63 inches||0.75 mm 0.0296inches||0.741 mm 0.0292inches||1.125mm 0.0443inches||1.1mm 0.043 inches||0.483 mm 0.019 inches||0.455 mm 0.0179 inches|
|7/8 mm 0.034inches||9 mm 0.35 inches||14 mm 0.55inches||0.875 mm 0.044 inches||0.866 mm 0.0341inches||1.312 mm 0.0517inches||1.285 mm 0.05inches||0.563 mm 0.0221inches||0.531 mm 0.0209 inches|
|1 mm 0.394inches||8 mm 0.315 inches||14 mm 0.55 inches||1 mm 0.0394 inches||0.99mm 0.0039 inches||1.5 mm 0.0591 inches||1.469mm 0.0586inches||0.627mm 0.0641 inches||0.591 mm 0.0626 inches|
Size Chart for Bolts (Metric)
|Nominal bolt size||Pitch||Shark diameter||Width across flats||Head thickness|
|M6||1 mm 0.0394inches||0.75 mm 0.0296inches||6 mm 0.2364inches||5.82mm 0.23inches||10 mm 0.394inches||9.78 mm 0.385inches||4.15 mm 0.163inches||3.85 mm 0.1517inches|
|M8||1.25 mm 0.0492inches||1 mm 0.0394inches||8 mm 0.3152inches||7.78 mm 0.307inches||13 mm 0.512inches||12.73 mm 0.5015inches||5.45 mm 0.214inches||5.15 mm 0.203inches|
|M10||1.5 mm 0.0591inches||1.25 mm 0.0492inches||10 mm 0.394inches||9.78 mm 0.389inches||16 mm 0.63 inches||15.73 mm 0.6197inches||6.58 mm 0.24inches||6.22 mm 0.245inches|
|M12||1.75 mm 0.0689inches||1.25 mm 0.0492inches||12 mm 0.4728inches||11.73 mm 0.462inches||18 mm 0.709inches||17.73 mm 0.699inches||7.68 mm 0.3026inches||7.32 mm 0.288inches|
|M14||2 mm 0.0788inches||1.5 mm 0.0591inches||14mm 0.5516inches||13.72 .mm 0.546inches||21 mm 0.8274inches||20.67 mm 0.8144inches||8.98 mm 0.354inches||8.62 mm 0.34inches|
|M16||2 mm 0.0788inches||1.5 mm 0.0591inches||16 mm 0.63 inches||15.73 mm 0.586inches||24 mm 0.9456inches||23.67 mm 0.9325inchs||10.18 mm 0.401inches||9.82 mm 0.387inches|
|M20||2.5 mm 0.0985inches||1.5 mm 0.0591inches||20 mm 0.788 inches||19.67 mm 0.774inches||30 mm 1.182inches||29.67 mm 1.167inches||12.715mm 0.5inches||12.85mm 0.506inches|
|M24||3 mm 0.1182inches||2mm 0.0788inches||24 mm 0.9456inches||23.67 mm 0.9325inches||36 mm 1.418inches||35.38 mm 1.294inches||15.22 mm 0.4inches||14.785mm 0.5826inches|
Metric clearance and tapping drill hole sizes chart
|Size||Clearance Hole||Thread Pitch (std)||Tapping Drill (std Pitch)||Thread Pitch (fine)||Tapping Drill (fine pitch)|
|M5||5.5 mm 0.22 inches||0.8 mm 0.0315 inches||4.2 mm 0.65 inches||n/l||n/l|
|M6||6.5 mm 0.27 inches||1.0 mm 0.0394 inches||5.0 mm 0.197 inches||0.75 mm 0.03 inches||5.25 mm 0.21 inches|
|M8||9 mm 0.35 inches||1.25 mm 0.05 inches||6.75 mm 0.266 inches||1.0 mm 0.0394 inches||7 mm 0.276 inches|
|M10||11 mm 0.43 inches||1.5 mm 0.06 inches||8.5 mm 0.335 inches||1.25 mm 0.05 inches||8.75 mm 0.45 inches|
|M12||14 mm 0.55 inches||1.75 mm 0.069 inches||10.25 mm 0.404 inches||1.5 mm 0.06 inches||10.5 mm 0.41 inches|
|M16||18 mm 0.71 inches||2.0 mm 0.08 inches||14 mm 0.55 inches||1.5 mm 0.06 inches||16.5 mm 0.65 inches|
|M20||22 mm 0.87 inches||2.5 mm 0.1 inches||17.5 mm 0.69 inches||1.5 mm 0.06 inches||20.5 mm 0.81 inches|
|M24||26 mm 1.02 inches||3.0 mm 0.12 inches||21 mm 0.827 inches||2.0 mm 0.08 inches||22 mm 0.87 inches|
|M30||32 mm 1.26 inches||3.5 mm 0.14 inches||26.5 mm 1.04 inches||2.0 mm 0.08 inches||28 mm 1.103 inches|
Standard Spanner and Allen Key Sizes Chart
|M5||8 mm 0.32 inches||4 mm 0.16 inches|
|M6||10 mm 0.4 inches||5 mm 0.2 inches|
|M8||13 mm 0.5 inches||6 mm 0.24 inches|
|M10||17 mm 0.66 inches||8 mm 0.32 inches|
|M12||19 mm 0.74 inches||10 mm 0.4 inches|
|M16||24 mm 0.95 inches||14 mm 0.55 inches|
|M20||30 mm 1.18 inches||17 mm 0.66 inches|
|M24||36 mm 1.42 inches||19 mm 0.74 inches|
|M30||46 mm 1.81 inches||n/l|
How to choose the size of the right bolt and what is the best size for you
Measuring Screws and Bolts (Using Size Chart for Bolts)
Knowing where to look for the diameter and length of the fasteners you need is a crucial first step in getting the right parts.
Diameters of Screws / Bolts
The distance between the outer threads on one side and the outer thread on the other side is used to determine the diameter of screws and bolts. This is known as the main diameter and is usually the bolt’s appropriate size. You can also find the minor diameter from one side to the other of the threads’ bottom hollow.
A number is typically used to identify the size of 1/4″ or less. A nominal measurement is what it’s called. These are the numbers, as well as the decimal equivalents.
Length of Screws / Bolts
The easiest method to remember how to measure length is to use the following formula: The length of a screw or bolt is measured from the flat part of the head to the tip or blunt end. Almost all screw heads are either flat on top or flat on the bottom.
Metric Bolt Measurement Standards
While different standardization, such as DIN, ISO, and JIS, may or may not require different dimensions for their respective bolts, measuring the bolts is generally the same, with only very few exceptions. The rare exceptions generally only affect how they are defined and not necessarily a change in the dimensions themselves. This is clearly seen in some pins.
Other Important Measurements
Some bolts have special features that can be required for proper sourcing. For example, hex head cap screws have a hexagon above the shank. The head itself is often measured by the WAF (width across the flats – the width across the head from one side to the adjacent side).
WAF can differ between standardization, such as between DIN 933 and ISO 4017. At most sizes, there is no difference, but at the M10, M12, M14, and M22 sizes The WAF is slightly different, which can affect its usefulness in some applications.
If you have enjoyed reading this article. On the bolt size, metric bolt measurement standards, and imperial bolt size, please don’t forget to share your experience in the comments section!
Learn more about different types of bolt and bolt sizes (video)
Frequently Asked Questions on Size Chart for Bolts
What bolt sizes are specified?
Pitch, diameter, and length in millimeters are used to specify the size of a metric bolt. For example, in M8-1.0*20, “M” stands for Metric thread designation, “8” stands for the nominal diameter (in millimeters), “1.0” stands for pitch, and “20” stands for length.
What do bolt size numbers mean?
The nominal or root (minor) diameter (mm) is the first number in each size, and the thread pitch (mm) is the second number (mm). Keep in mind that the nominal bolt diameter is taken from the bottom of the threads, not the top which would be the major diameter.
What does the M mean in bolt sizes?
The “M” designation for metric screws shows the nominal outer diameter of the screw thread, in millimeters
Is M6 or M8 bigger?
In terms of width, the new M8 is only 0.27 inches wider than the M6. The new BMW M8 is shorter than the M6, with the M8 bolt measuring 53.62 inches and the M6 measuring 54.10 inches.
Does M10 mean 10mm?
M10 means a 10-millimeter outer diameter for the bolt or whatever piece it is.
An overview of bolts, including common bolt materials, numerous types of bolts, and typical bolt specifications and measurements. With the help of illustrations and a Bolt Size Chart, you may also learn about Bolt Size, Bolt Head Size, and their differences. Bolt dimensions and thread pitch are given in the Bolt Size Chart’s imperial and metric units.
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