" Steel Solutions for the Next Generation "

Choosing the right nut and bolt size for your application is crucial. At Renox Impex, we understand the importance of using the right sizes for your projects, whether metric or standard. Our nut bolt size chart is designed to help you find the perfect selection.

What is bolt size?

Bolt size refers to the dimensions of a bolt, which include the diameter, length, and thread pitch. These measurements ensure that the bolt fits properly in its application. Bolt sizes are specified in metric (millimetres) or imperial (inches) units.

The diameter of a bolt is measured across the bolt shank or threaded area, while the length is measured from the tip to where the shank meets the head. If the bolt is partially threaded, you can also measure the thread length. For detailed dimensions and standard sizes, refer to a bolt size chart that includes both imperial and metric measurements.

Bolt size

Bolt Size Chart

Here is the following standard bolt size chart that covers metric and imperial measurements for all the important dimensions of a bolt.

Download the PDF of Standard Bolt Sizes in mm

Metric Bolt Size Chart

Size Outside Diameter (mm) Thread Pitch (mm) Coarse/Fine Designation
M1.6 x 0.35 1.6 0.35 Coarse
M1.6 x 0.2 1.6 0.2 Fine
M1.7 x 0.35 1.7 0.35 Coarse
M1.8 x 0.35 1.8 0.35 Coarse
M1.8 x 0.2 1.8 0.2 Fine
M2 x 0.4 2 0.4 Coarse
M2 x 0.25 2 0.25 Fine
M2.2 x 0.45 2.2 0.45 Coarse
M2.2 x 0.25 2.2 0.25 Fine
M2.5 x 0.45 2.5 0.45 Coarse
M2.5 x 0.35 2.5 0.35 Fine
M2.6 x 0.45 2.6 0.45 Coarse
M3 x 0.5 3 0.5 Coarse
M3 x 0.35 3 0.35 Fine
M3.5 x 0.6 3.5 0.6 Coarse
M3.5 x 0.35 3.5 0.35 Fine
M4 x 0.7 4 0.7 Coarse
M4 x 0.5 4 0.5 Fine
M4.5 x 0.75 4.5 0.75 Coarse
M4.5 x 0.5 4.5 0.5 Fine
M5 x 0.8 5 0.8 Coarse
M5 x 0.5 5 0.5 Fine
M5.5 x 0.5 5.5 0.5 Fine
M6 x 1 6 1 Coarse
M6 x 0.75 6 0.75 Fine
M7 x 1 7 1 Coarse
M8 x 1.25 8 1.25 Coarse
M8 x 1 8 1 Fine
M9 x 1.25 9 1.25 Coarse
M9 x 1 9 1 Fine
M10 x 1.5 10 1.5 Coarse
M10 x 1 10 1 Fine
M10 x 0.75 10 0.75 Fine
M11 x 1 11 1 Fine
M11 x 1.5 11 1.5 Coarse
M12 x 1 12 1 Fine
M12 x 1.75 12 1.75 Coarse
M14 x 1 14 1 Fine
M14 x 2 14 2 Coarse
M15 x 1 15 1 Fine
M16 x 1 16 1 Fine
M16 x 2 16 2 Coarse
M17 x 1 17 1 Fine
M18 x 1.5 18 1.5 Fine
M18 x 2.5 18 2.5 Coarse
M20 x 1 20 1 Fine
M20 x 2.5 20 2.5 Coarse
M22 x 1 22 1 Fine
M22 x 2.5 22 2.5 Coarse
M24 x 1 24 1 Fine
M25 x 1 25 1 Fine

Imperial Bolt Size Chart

Size Outside Diameter (OD) Threads Per Inch (TPI) Coarse/Fine Designation
#0 - 80 0.0600 80 UNF
#1 - 64 0.0730 64 UNC
#1 - 72 0.0730 72 UNF
#2 - 56 0.0860 56 UNC
#2 - 64 0.0860 64 UNF
#3 - 48 0.0990 48 UNC
#3 - 56 0.0990 56 UNF
#4 - 40 0.1120 40 UNC
#4 - 48 0.1120 48 UNF
#5 - 40 0.1250 40 UNC
#5 - 44 0.1250 44 UNF
#6 - 32 0.1380 32 UNC
#6 - 40 0.1380 40 UNF
#8 - 32 0.1640 32 UNC
#8 - 36 0.1640 36 UNF
#10 - 24 0.1900 24 UNC
#10 - 32 0.1900 32 UNF
#12 - 24 0.2160 24 UNC
#12 - 28 0.2160 28 UNF
1/4" - 20 0.2500 20 UNC
1/4" - 28 0.2500 28 UNF
5/16" - 18 0.3125 18 UNC
5/16" - 24 0.3125 24 UNF
3/8" - 16 0.3750 16 UNC
3/8" - 24 0.3750 24 UNF
7/16" - 14 0.4375 14 UNC
7/16" - 20 0.4375 20 UNF
1/2" - 13 0.5000 13 UNC
1/2" - 20 0.5000 20 UNF
9/16" - 12 0.5625 12 UNC
9/16" - 18 0.5625 18 UNF
5/8" - 11 0.6250 11 UNC
5/8" - 18 0.6250 18 UNF
3/4" - 10 0.7500 10 UNC
3/4" - 16 0.7500 16 UNF
7/8" - 9 0.8750 9 UNC
7/8" - 14 0.8750 14 UNF
1" - 8 1.0000 8 UNC
1" - 12 1.0000 12 UNF
1" - 14 1.0000 14 UNS

Notes:

  • Metric sizes are denoted by "M" followed by the nominal size in mm.
  • Standard (inch) sizes are denoted by the nominal size in inches or fractions.
  • Pitch is the distance between adjacent threads (mm for metric, threads per inch for standard).
  • Major diameter is the largest outer diameter of the thread.
  • Minor diameter is the smallest inner diameter of the thread.
  • Nut size is the width across the flats of the nut.

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Check Standard Bolt Sizes Chart Pdf, Metric Bolt Size Chart.

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Nut Bolt Size Chart in mm

Size Bolt Diameter (mm) Nut Width (mm) Nut Height (mm) Bolt Head Width (mm) Bolt Head Height (mm)
M4 4 7 3.2 7 2.8
M5 5 8 4.7 8 3.5
M6 6 10 5.2 10 4.0
M8 8 13 6.8 13 5.3
M10 10 17 8.4 17 6.4
M12 12 19 10.8 19 7.5
M14 14 22 12.8 22 8.8
M16 16 24 14.8 24 10.0
M18 18 27 15.8 27 11.5
M20 20 30 18.0 30 12.5
M22 22 34 19.4 34 14.0
M24 24 36 21.5 36 15.0

How to Use the Bolt Size Chart

  • » Identify the Bolt Diameter: Measure the diameter of the bolt you have or need.
  • » Match the Thread Pitch: Ensure that the thread pitch of the bolt matches the corresponding pitch in the chart.
  • » Select the Correct Nut Size: Use the nut width across flats to choose a nut that fits the bolt diameter.
  • » Verify Nut Height: Confirm that the nut height is suitable for your application, ensuring a secure fit.

Find the Perfect Fit: Check Out Our Spanner Size Chart for bolts

Frequently Asked Questions (FAQs):

  • How to measure bolt size?

    Bolt sizes are measured using three key dimensions: diameter, thread pitch, and length. First, the diameter of the bolt's shank is set, which can be millimeters for metric bolts and inches for imperial bolts. After that, the thread pitch is determined as the number of threads per inch or the distance between the threads. Last, the length of the bolt is defined from below the head to its tip. These measurements help to guarantee that the bolt will fit the desired application and have the correct strength and rigidity.

    Find out more on How bolt sizes are measured in our detailed guide.

  • Difference between imperial and metric bolts

    Metric bolts are measured in millimeters, whereas imperial bolts are measured in inches. The main differences include:

    • Thread Pitch: Metric bolts use a pitch in millimeters (distance between threads), while imperial bolts use threads per inch (TPI).
    • Diameter Measurement: Metric bolts indicate diameter in millimeters; imperial bolts use fractions of an inch.
    • Size Notation: Metric sizes are denoted as M followed by the diameter (e.g., M10), whereas imperial sizes use a number or fractional notation (e.g., 3/8").

    Understand these differences in our Imperial vs Metric Bolts explanation

  • What does m mean in bolt sizes?

    The 'M' in bolt sizes means the bolt has a metric thread. The number after 'M' shows the bolt's diameter in millimeters. For example, an 'M8' bolt is 8 mm in diameter. This system is used worldwide, except in countries primarily using the imperial system (like the US).

  • How can I ensure the accuracy of my measurements when using a nut bolt size chart?

    To get accurate measurements using a nut and bolt size chart, use tools like calipers or a micrometer. Measure the bolt’s diameter and length carefully, then compare your results to the chart. If unsure, compare the bolt physically to known sizes or consult a specialist.

  • What are the differences between coarse, fine, and extra fine thread pitches

    Coarse threads have a larger pitch with fewer threads per inch, making them durable and resistant to stripping. Fine threads feature a smaller pitch, allowing for finer adjustments and greater strength in both tension and shear. Extra fine threads are even more precise, ideal for applications requiring high precision and exact adjustments.

Applications of Different Bolt Sizes

Oil & Gas
Industry

Power Plant
Generation

Marine
Industry

Petrochemical
Industry

Chemical
Industry

Aerospace
Industry

Sugar
Industry

  • Small Bolts (e.g., M4, 1/4"): These are typically used in electronics, light mechanical work, or for fastening thin materials.
  • Medium Bolts (e.g., M8, 3/8"): Often found in automotive parts, machinery, and general construction.
  • Large Bolts (e.g., M16, 5/8"): Commonly employed in heavy-duty scenarios like structural engineering, large machines, and major infrastructure projects.
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