Fasteners are the backbone of construction, machinery, automotive, and DIY projects. Among them, screws are the most common type, used everywhere from household furniture to heavy industrial equipment. Screws come in many different systems of measurement, but one of the most widely used worldwide is the metric system, denoted by the letter M.
The M screw size chart is a quick reference that helps builders, engineers, and technicians select the correct screw dimensions. This guide will explain what M screws are, how to read their sizes, and provide a complete chart of common metric screw sizes.
What Are M Screws?
The “M” in M screws stands for metric, and it represents the nominal diameter of the screw in millimeters. For example:
M3 screw → 3 mm in diameter
M5 screw → 5 mm in diameter
M10 screw → 10 mm in diameter
Unlike inch-based screws used in some countries (such as the U.S.), metric screws are globally standardized, making them easier to work with in international projects.
Each M screw size is defined by three key measurements:
Nominal Diameter (M) – Thickness of the screw shaft in millimeters.
Thread Pitch (P) – The distance between threads, measured in millimeters.
Length (L) – Total screw length from the head to the tip.
Example: M8 × 1.25 × 40 means a screw with 8 mm diameter, 1.25 mm thread pitch, and 40 mm length.
Why Use an M Screw Size Chart?
When selecting screws, accuracy is critical. The wrong size can cause:
Loose fittings
Stripped threads
Structural weakness
Damage to parts
An M screw size chart provides exact dimensions for each screw size, ensuring the correct fit every time. It helps engineers, technicians, and DIY enthusiasts save time and avoid costly errors.
📌 For readers wanting advanced knowledge, 👉 American Screw Size Chart 2025: Complete Guide
M Screw Size Chart (Common Sizes)
Below is a practical M screw size chart showing standard metric screw dimensions:
| Screw Size | Thread Pitch (mm) | Head/Wrench Size (mm) | Typical Length Range (mm) |
|---|---|---|---|
| M2 | 0.4 | 4 | 3 – 20 |
| M2.5 | 0.45 | 5 | 4 – 25 |
| M3 | 0.5 | 5.5 | 5 – 30 |
| M4 | 0.7 | 7 | 6 – 40 |
| M5 | 0.8 | 8 | 8 – 50 |
| M6 | 1.0 | 10 | 10 – 60 |
| M8 | 1.25 | 13 | 12 – 80 |
| M10 | 1.5 | 16 | 16 – 100 |
| M12 | 1.75 | 18 | 20 – 120 |
| M14 | 2.0 | 21 | 25 – 140 |
| M16 | 2.0 | 24 | 30 – 160 |
| M20 | 2.5 | 30 | 40 – 200 |
| M24 | 3.0 | 36 | 50 – 250 |
M Screw Size Chart PDF
The M Screw Size Chart PDF provides a quick reference for common metric screw dimensions, including thread pitch, head or wrench size, and typical length range. It’s designed for engineers, DIY enthusiasts, and professionals who need accurate measurements at a glance. This chart ensures easy selection of the right screw size for various mechanical, construction, and technical projects.
How to Read the Chart
Let’s take an M6 screw as an example:
M6 → Nominal diameter is 6 mm.
Thread Pitch 1.0 mm → Threads are spaced 1 mm apart.
Head Size 10 mm → Requires a 10 mm spanner or driver.
Length Range → Available from 10 mm up to 60 mm.
This ensures you choose the correct screw and matching nut for your project.
📌 For readers wanting advanced knowledge, 👉 Screw Size Chart: Complete Guide
Types of Threads in Metric Screws
Metric screws can come in three types of threads:
Coarse Thread (standard) – Most common, strong, and resistant to wear.
Fine Thread – Provides better tension and resistance to loosening.
Extra Fine Thread – Used in precision applications such as aerospace or electronics.
For example:
M10 × 1.5 → Standard coarse thread
M10 × 1.25 → Fine thread
M10 × 1.0 → Extra fine thread
Applications of Metric Screws
Metric screws are found in nearly every industry:
Construction → Securing panels, beams, and structures.
Automotive → Used in engines, body panels, and suspensions.
Electronics → Common in laptops, phones, and other devices.
Furniture → Widely used in flat-pack furniture assembly.
Machinery → Essential in equipment and mechanical tools.
Choosing the Right M Screw Size
To select the correct screw size:
Measure the Hole Diameter – Match it with the screw’s nominal diameter.
Check Thread Pitch – Ensure it matches with corresponding nuts.
Select Correct Length – Length should match material thickness.
Consider Material – Choose stainless steel for outdoor use, carbon steel for indoor.
Load Capacity – Larger screws handle greater loads.
Advantages of Using Metric Screws
Globally standardized → easy to source worldwide.
Precise sizing in millimeters.
Strong and reliable fastening.
Wide variety of materials (stainless, galvanized, alloy).
Suitable for both heavy-duty and precision applications.
Common Mistakes to Avoid
Mixing metric with imperial screws – They are not interchangeable.
Ignoring thread pitch – Even if diameter matches, pitch mismatch prevents fit.
Wrong length selection – Too short = weak fastening, too long = damage to material.
Using wrong driver – Can strip the screw head.
Conclusion
The M Screw Size Chart is an essential tool for anyone working with fasteners. From small electronics to heavy construction projects, using the right screw ensures safety, stability, and efficiency.
By understanding screw dimensions, thread pitches, and applications, you’ll always choose the correct fastener. Keep this chart handy—it will save time, prevent costly errors, and make every project smoother.
📌 For readers wanting advanced knowledge, 👉 Drill Chart 2025: Complete Guide
FAQs Related to M screw Sizes
What is an M screw?
An M screw is a metric screw defined by the letter “M” followed by its nominal diameter in millimeters. For example, M6 means the screw has a 6mm diameter. These screws are widely used in construction, automotive, and machinery due to their precise sizing. Metric screws follow ISO standards, making them interchangeable across industries and countries, ensuring consistency and reliability in fastening applications.
How do I read an M screw size chart?
An M screw size chart lists screw diameters, thread pitch, wrench or head size, and typical length ranges. For example, M8 means an 8mm diameter, with a standard pitch of 1.25mm. The chart helps users quickly identify the correct screw size for their project, preventing mismatches. By referencing the chart, builders and engineers can select the right fastener efficiently and avoid costly installation errors.
Why is thread pitch important in M screws?
Thread pitch indicates the distance between screw threads, measured in millimeters. It determines how tightly or loosely the screw fits into a nut or tapped hole. Choosing the wrong pitch can cause stripping or weak fastening. Fine-pitch threads are ideal for precision applications, while coarse-pitch threads work better in general construction. The M screw size chart ensures the right thread pitch is selected for every job.
What are the common applications of M screws?
M screws are used in a wide range of applications including automotive assemblies, construction projects, furniture manufacturing, and mechanical engineering. Smaller sizes like M2 or M3 are common in electronics, while larger ones like M16 or M20 are used in heavy machinery. The chart helps users match screw sizes with appropriate tasks, ensuring safe fastening, durability, and efficiency across industries that depend on metric fasteners daily.
How do I choose the correct length for an M screw?
The correct length of an M screw depends on the material thickness and the load requirements of the project. The M screw size chart provides typical length ranges to guide users. For instance, an M6 screw is typically 10–60mm long. Selecting the right length ensures proper grip and prevents over-penetration. Builders should always measure material depth and compare it against chart values for accurate selection.
Are M screws standardized worldwide?
Yes, M screws follow the ISO metric standard, making them universally recognized and interchangeable across countries. This global standardization ensures that an M6 screw manufactured in Europe will match an M6 nut from Asia or the U.S. Such consistency reduces supply chain issues, supports international trade, and simplifies repairs. The M screw size chart provides the standard measurements that guarantee this uniformity worldwide for fasteners.
What tools are required for M screws?
M screws typically require spanners, wrenches, or socket sets that match the head size indicated in the chart. For instance, an M10 screw needs a 16mm wrench. Power tools like drills and drivers are also used for faster installation. The size chart helps users select the right tool quickly, avoiding damage to the screw head or improper fastening. Using correct tools ensures both safety and durability.