Conversion Chart

Your Complete Fastener Conversion Chart & Guide

When you’re working on a project, whether it’s large-scale manufacturing or a small repair, choosing the right fastener size is critical. However, when fasteners come in both U.S. imperial and metric measurements, navigating between the two systems can quickly become confusing. At Fasteners Etc., Inc., we want to make your processes easier, so we’ve put together a handy fastener conversion chart for you to reference during your work.

This page is designed to make your work simpler, faster, and more accurate. With clear conversions between imperial fasteners and metric fasteners and expert tips from our knowledgeable team, you’ll always have the right information at your fingertips.

Simplify Your Fastener Projects with Accurate Conversions

Every project requires precision. Using the wrong fastener size can lead to material damage, compromised structural integrity, or wasted time. That’s why quick and reliable conversions matter.

Our fastener conversion chart eliminates the guesswork. It helps you:

• Translate between inch-based (imperial) and millimeter-based (metric) measurements
• Avoid costly mistakes by selecting the correct screw, bolt, or stud size
• Save time on the job site with accurate reference points

Whether you’re a contractor handling bulk orders, a maintenance professional sourcing replacement screws, a DIYer renovating or repairing, or a small business owner, this conversion table is your go-to resource for getting it right the first time.

Fastener Conversion Chart: Fraction, Inch, and Millimeter Table

Use this table to simplify the conversion process. Simply look at the size of the fastener you have, whether it’s in inches or millimeters, and find the corresponding fastener size in the other measurement system.

If you’re unsure of the fastener size, you may have to use digital calipers to get the diameter and length. These tools are handheld measuring instruments that use a digital encoder to display measurements on a screen, offering accurate and easy-to-read results.

This chart can be used by workers in various industries, including automotive, manufacturing, aerospace, and more. It’s also helpful if you’re doing a DIY project and have fasteners of different systems that you aren’t sure how to convert.

Understanding Fastener Measurement Systems

Nothing screws up your productivity and motivation faster than realizing you used the wrong size fastener. Avoid this mistake by clearly understanding the difference between the two commonly used systems and their measurements.

U.S. Imperial vs. Metric: Decoding Fastener Sizes

Fasteners are measured using two primary systems: U.S. imperial and metric. Understanding how they differ is the first step to ensuring accuracy in your projects.

The imperial system is common in the United States. It uses non-decimal-based units like inches, fractions, and gauge numbers to define screw sizes. Threading often follows Unified National Coarse (UNC) and United National Fine (UNF) standards to define threads per inch.

The metric system is used internationally and is the global standard for measurement. However, it is increasingly being used by U.S. industries that have global suppliers. The metric system is decimal-based and uses prefixes like kilo and milli to denote powers of ten. In this system, measurements are given in millimeters (mm) for both diameter and length, and the thread pitch is explicitly defined by the distance between threads.

While these systems differ, both are widely used across industries. That’s why conversion tools are so valuable. They allow you to easily cross-reference fastener sizes between the two systems, ensuring a perfect fit. However, because of the different governing bodies, there may be some variance. These bodies include:

• American National Standards Institute (ANSI)
• ASTM International
• Industrial Fasteners Institute (IFI)
• SAE International
• International Organization for Standardization (ISO)

Our conversion chart provides the inch equivalent and metric conversion you need for screws, bolts, studs, and more. This makes it quick and easy to determine which you should be using, helping to prevent mistakes and make your process smoother.

Need a Specific Fastener Size? Request a Quote for Bulk Orders

Whenever you’re working on a project, having the right fastener size is vital. Make sure you can correctly convert imperial screws or bolts to metric and back with our conversion chart.

However, sometimes even with the best conversion tools, you’ll find you don’t have a good equivalent in stock. If you need a fastener that’s harder to find or need it in large quantities, Fasteners Etc., Inc. can help. We work with both large-scale industrial clients and small businesses, tailoring solutions to fit your needs. Whether you’re sourcing thousands of bolts for production or just a handful of specialty screws, our team is here to help. We’ll make sure you get the right solution for your project, delivered with the personal service you expect from us.

As a veteran-owned business, we pride ourselves on integrity, excellence, and personalized service. Our team combines decades of knowledge with a customer-first approach. This allows us to deliver bulk ordering and competitive quotes for projects of any size. We also offer a wide inventory of fasteners, ensuring you get the right part when you need it. Request a quote if you have any questions about bulk orders. Do you want to learn more about our fasteners? Contact us today.