A cable gland size chart is your essential translation tool, matching a cable's outer diameter (OD) to the correct gland thread size—be it Metric (M), PG, or NPT. For any engineer or technician in the field, this is the go-to reference to guarantee a secure, environmentally sealed, and totally reliable connection. Using a chart takes the guesswork out of the equation, ensuring the gland's clamping range is a perfect fit for the cable.
Your Quick-Reference Cable Gland Size Chart
When you're on the job and just need the right size, fast, this is the chart for you. We've consolidated the most common gland sizes into one quick lookup table for professionals who need immediate answers. Use it to quickly confirm the right gland for your application, and then dive into the more detailed sections later for the nitty-gritty on technical specs and installation tips.
The three main thread standards you'll run into—Metric, PG, and NPT—are shown below. Getting familiar with their symbols is key for reading schematics and identifying hardware on-site.
Below is the quick lookup table to match your cable's outer diameter with the appropriate gland size across these common standards.
Pro Tip: For the best possible seal and strain relief, always pick a gland where your cable's OD lands comfortably in the middle of its specified clamping range. Avoid pushing the limits at the extreme minimum or maximum.
Quick Lookup Cable Gland Sizing
Here’s a straightforward table to match your cable's outer diameter (OD) with the most common Metric, PG, and NPT gland sizes. It's perfect for a quick check before you order or install.
| Cable OD Range (mm) | Recommended Metric (M) Size | Recommended PG Size | Equivalent NPT Size |
|---|---|---|---|
| 3 – 6.5 mm | M12 | PG7 | 3/8" |
| 6 – 12 mm | M16 / M20 | PG9 / PG11 | 1/2" |
| 10 – 14 mm | M20 | PG13.5 | 1/2" |
| 13 – 18 mm | M25 | PG16 / PG21 | 3/4" |
| 16 – 25 mm | M32 | PG21 / PG29 | 1" |
| 22 – 32 mm | M40 | PG29 / PG36 | 1 1/4" |
| 30 – 38 mm | M50 | PG36 / PG42 | 1 1/2" |
| 34 – 44 mm | M63 | PG48 | 2" |
This table covers the majority of standard applications you'll encounter. For less common sizes or more detailed specifications on materials and IP ratings, be sure to check the comprehensive charts further down in this guide.
Decoding Cable Gland Thread Standards
Before you even glance at a cable gland size chart, you have to know which thread standard your equipment uses. It’s a common and surprisingly costly mistake to get this wrong—Metric, PG, and NPT threads are not interchangeable. Each standard has its own unique thread profile and history, making compatibility the absolute first thing you need to verify.
Getting this right ensures the gland doesn't just fit your cable, but also interfaces correctly with your enclosure, junction box, or machine. A mismatched thread won't seal properly, which immediately compromises the system's Ingress Protection (IP) rating and its overall integrity.
Metric (M) Threads: The Global Standard
Defined by standards like EN 60423, Metric threads are what you'll find on most modern industrial equipment across the globe. They're simple to identify by the "M" prefix, followed by the nominal outer diameter in millimeters—think M20 or M32.
Metric threads have a parallel profile, which means the threads themselves don't create the seal. Instead, they rely on an O-ring or a flat sealing washer squished between the gland's body and the enclosure wall to create a liquid-tight barrier.
- Profile: Symmetrical V-shape with a 60-degree angle.
- Sealing: Always needs a separate sealing washer or O-ring.
- Application: The dominant choice for new equipment in Europe, Asia, and increasingly, North America.
Panzergewinde (PG) Threads: The Legacy System
Panzergewinde (PG) is an older German thread standard. While it's now obsolete for new designs, you'll run into it all the time when servicing or retrofitting machinery built before the early 2000s.
Just like Metric threads, PG threads are parallel. The critical difference is their thread angle is a much flatter 80 degrees, making them completely incompatible with Metric-threaded holes. You'll absolutely need a conversion chart if you're replacing an old PG gland with a modern Metric one.
PG threads were officially phased out by German standards back in 2000 and replaced by the Metric system. But because they're still out there on so much existing equipment, any good cable gland size chart has to include them.
National Pipe Thread (NPT): The Tapered Standard
National Pipe Thread (NPT) is the American standard for tapered threads used on pipes and fittings. Unlike the parallel Metric and PG styles, NPT threads are engineered to create a seal through pure mechanical interference. As you tighten the gland, the tapered male and female threads wedge together, forming an incredibly tight, robust connection.
This tapered design is its signature feature. While it’s good practice to use a thread sealant or PTFE tape to guarantee a 100% leak-proof joint, the threads themselves are doing most of the work.
Key NPT Characteristics:
- Tapered Profile: The threads get narrower along their length, creating a seal by binding together under torque.
- Self-Sealing: Designed to seal through thread deformation as it's tightened down.
- Primary Use: Mostly found in North American setups, especially in process control and hazardous locations where a rock-solid seal is non-negotiable.
Metric (M) Cable Gland Sizing and Specifications
When you're working with modern industrial and commercial electrical installations, you'll almost certainly be using Metric cable glands. These are the international standard, designated by the letter "M" and a number (like M20 or M32), and are governed by standards such as EN/IEC 60423.
Their design features a fine, parallel thread that provides a rock-solid mechanical connection. However, it's important to remember this thread doesn't create the seal on its own.
To achieve a proper IP (Ingress Protection) rating, you need a separate sealing element—usually an O-ring or a flat washer—that gets compressed between the gland's body and the enclosure. The number right after the "M" simply tells you the nominal outer thread diameter in millimeters.
Understanding the Metric Cable Gland Size Chart
For any engineer, a metric cable gland size chart is an essential tool. It's the bridge between a cable's outer diameter and the right gland size, taking the guesswork out of getting a perfect fit. The chart maps each M-size to three crucial specs you need to check for a reliable installation.
- Cable OD Clamping Range (mm): This tells you the minimum and maximum cable diameter the gland’s internal seal can securely grip and seal.
- Clearance Hole Diameter (mm): This is the precise size of the hole you need to drill or punch in your enclosure so the gland body can pass through cleanly.
- Thread Pitch (mm): This defines the distance between the threads. For most metric glands up to M63, a 1.5mm pitch is standard, which is great for ensuring compatibility between glands and locknuts, even from different brands.
Let’s say you’re working with a cable that has a 13mm outer diameter. Grabbing an M20 gland is the right move, as its typical 6-13mm clamping range accommodates the cable perfectly and guarantees a liquid-tight seal. Using a detailed chart isn't just a suggestion; it's absolutely critical for system integrity.
Detailed Metric Thread Specifications
The table below is your go-to reference for common Metric cable gland sizes. Use it to match your cable's measured OD to the right gland and to confirm the clearance hole and thread specs for your panel. For an even deeper dive, you can find more resources covering metric cable glands.
Metric (M) Thread Cable Gland Specifications
| Metric Size | Cable OD Clamping Range (mm) | Clearance Hole Ø (mm) | Thread Pitch (mm) |
|---|---|---|---|
| M12 x 1.5 | 3 – 7 mm | 12.2 mm | 1.5 mm |
| M16 x 1.5 | 4 – 10 mm | 16.2 mm | 1.5 mm |
| M20 x 1.5 | 6 – 13 mm | 20.2 mm | 1.5 mm |
| M25 x 1.5 | 8 – 17 mm | 25.2 mm | 1.5 mm |
| M32 x 1.5 | 15 – 21 mm | 32.2 mm | 1.5 mm |
| M40 x 1.5 | 19 – 28 mm | 40.2 mm | 1.5 mm |
| M50 x 1.5 | 27 – 35 mm | 50.2 mm | 1.5 mm |
| M63 x 1.5 | 34 – 45 mm | 63.2 mm | 1.5 mm |
Important Takeaway: Always measure the cable's actual outer diameter with digital calipers. Don't just rely on the manufacturer's datasheet. Production tolerances can cause slight variations in cable size that are big enough to cause a sealing issue.
While metric glands are used everywhere, it's interesting to see where the growth is. The data cables segment, for instance, is the fastest-growing category with a CAGR of 9.5%. This is driven by the global expansion of data centers and 5G networks, where specialized glands are essential for protecting delicate fiber optic connections. You can find more insights on this trend over at Cognitive Market Research.
PG and NPT Thread Size Charts
While Metric threads are the go-to for most modern equipment, any comprehensive cable gland size chart needs to cover the legacy Panzergewinde (PG) and North American National Pipe Thread (NPT) standards. If you're a maintenance tech or an engineer, you'll inevitably run into these thread types, especially when servicing older machinery or working on equipment built for specific markets. Knowing how to size them is critical for any successful retrofit or repair.
The PG standard has been officially obsolete since 2000, but don't be fooled—it’s still incredibly common on European-made machines from the late 20th century. Unlike Metric threads, the PG size number doesn't directly relate to its outer diameter, making a reference chart an absolute necessity for proper identification.
Panzergewinde (PG) Size Chart
Use this table to match a PG gland to your cable's outer diameter. I've also included the closest Metric equivalent, which is crucial information when you're planning to upgrade or replace a worn-out component on an older system.
| PG Size | Cable OD Clamping Range (mm) | Clearance Hole Ø (mm) | Closest Metric Equivalent |
|---|---|---|---|
| PG7 | 3 – 6.5 mm | 12.5 mm | M12 |
| PG9 | 4 – 8 mm | 15.2 mm | M16 |
| PG11 | 5 – 10 mm | 18.6 mm | M16 / M20 |
| PG13.5 | 6 – 12 mm | 20.4 mm | M20 |
| PG16 | 10 – 14 mm | 22.5 mm | M20 / M25 |
| PG21 | 13 – 18 mm | 28.3 mm | M25 |
| PG29 | 18 – 25 mm | 37.0 mm | M32 |
| PG36 | 22 – 32 mm | 47.0 mm | M40 |
| PG42 | 30 – 38 mm | 54.0 mm | M50 |
| PG48 | 34 – 44 mm | 59.3 mm | M63 |
National Pipe Thread (NPT) Size Chart
You'll find NPT threads mostly in the United States and Canada, and they're easy to spot because of their tapered profile. This design is what makes them different; as you tighten them, the threads wedge together to form a seal through mechanical interference. This is a major departure from the parallel threads of Metric and PG standards.
This self-sealing ability makes NPT a top choice for hazardous locations and process control applications where you need a rock-solid, vibration-resistant connection. If you're new to this standard and want to dig into the technical details, you can get up to speed with our complete guide on NPT thread dimensions and their unique features.
The table below maps the common NPT sizes to their cable clamping ranges. Just remember, NPT sizes are based on the nominal pipe size, not the actual thread diameter.
Technical Note: The NPT standard specifies a taper of 1° 47' (one degree, forty-seven minutes). It’s this precise angle that ensures the male and female threads form an increasingly tight seal, effectively locking together as you apply torque.
| NPT Size | Cable OD Clamping Range (mm) | Nominal Thread OD (inches) |
|---|---|---|
| 1/4" | 3 – 6 mm | 0.540" |
| 3/8" | 3 – 7 mm | 0.675" |
| 1/2" | 6 – 12 mm | 0.840" |
| 3/4" | 13 – 18 mm | 1.050" |
| 1" | 18 – 25 mm | 1.315" |
| 1 1/4" | 22 – 32 mm | 1.660" |
| 1 1/2" | 30 – 38 mm | 1.900" |
| 2" | 34 – 44 mm | 2.375" |
Having quick access to both PG and NPT sizing charts is indispensable for any professional working with a diverse range of industrial equipment. These tables cut through the guesswork and help you specify the right connection every time, no matter how old the system is or where it came from.
How to Measure and Select the Correct Cable Gland
To get the most out of any cable gland size chart, you have to start with one non-negotiable step: accurate measurement. Getting the right fit isn't just about slipping a cable through a hole. It's about creating a rock-solid, environmentally sealed connection that shields your equipment from dust, water, and mechanical strain. One wrong choice here can compromise the entire system's integrity, leading to expensive downtime and headaches you don't need.
The whole process is about turning raw data into a confident decision. If you follow a structured approach, you can take all the guesswork out of the equation and nail the perfect gland selection for your application, every single time. And it all begins with a good pair of digital calipers.
Step 1: Accurately Measure the Cable Outer Diameter
The single most critical measurement in this entire process is the cable's outer diameter (OD). Manufacturer datasheets will give you a nominal OD, but production tolerances mean the actual size can vary a bit. Never rely on spec sheets alone.
That's why you should always use a digital caliper for a precise reading. I recommend measuring the cable in a few different spots and using the average to account for any slight ovality. This one action is the foundation for building a reliable, lasting seal.
Step 2: Follow the Selection Checklist
Once you have your precise OD measurement, you can confidently run through the key selection criteria. This simple checklist makes sure you don't miss any critical details, guiding you from the cable measurement to the final component choice. Proper selection of cable glands is a cornerstone for reliable electrical solutions for industrial needs, ensuring both safety and long-term performance.
Here’s a simple four-step process for a perfect match:
- Confirm the Cable OD: Take your measured OD and find where it fits within the "Clamping Range" column on the right cable gland size chart (Metric, PG, or NPT).
- Identify the Thread Type: Look at the mounting hole on your enclosure or equipment. Is it a parallel thread like Metric (M) or PG, or is it a tapered NPT thread? These are not interchangeable, so get it right.
- Define Environmental Needs: What level of Ingress Protection (IP) rating do you need? Is basic dust protection (IP54) enough, or do you need a gland that can be fully submerged (IP68)? Also, think about the material—nylon for general use, nickel-plated brass for extra durability, or stainless steel for corrosive environments.
- Pinpoint the Gland: Use the charts to find the specific gland that checks all your boxes: clamping range, thread type, and material.
Pro Tip: For the most secure and reliable seal, always pick a gland where your cable's outer diameter falls somewhere near the middle of its specified clamping range. Try to avoid sizes where your cable is at the absolute minimum or maximum limit. That can lead to an improper seal or put too much stress on the cable jacket.
Putting It into Practice
Let's walk through a common scenario. Say you have a power cable with a measured OD of 11.5 mm. It needs to be installed in a modern junction box with a pre-tapped M20 hole, and the whole setup is in a wet environment.
- Cable OD: 11.5 mm.
- Thread Type: M20 (Metric).
- Environment: Wet, so it needs at least an IP67 rating.
Looking at a Metric chart, you’ll see an M20 gland typically has a clamping range of 6-13 mm. Your 11.5 mm cable fits beautifully within this range, not too close to either extreme, which is perfect for a strong seal. You would then specify an M20 cable gland made from nickel-plated brass with an IP68 rating to ensure it holds up over the long haul. This systematic approach guarantees every connection is secure, protected, and built to last.
Choosing the Right Material and IP Rating
Picking the right size from a cable gland size chart is just the first step. To ensure long-term reliability, you have to match the gland's material and environmental protection to where it will be installed. A perfect fit doesn't mean much if the gland can't survive its surroundings, so you need to think about things like chemical exposure, temperature swings, and moisture.
The material of the cable gland has a direct impact on its durability and what it can be used for. A poor choice here can lead to early failure, putting the entire installation at risk.
Common Cable Gland Materials
Three materials really dominate the market, and each one brings something different to the table for various industrial jobs.
- Nylon (Polyamide): These are lightweight, corrosion-resistant, and won't break the bank. Nylon glands are a great fit for general-purpose indoor setups like control panels and automation equipment, as long as they aren't exposed to harsh chemicals or extreme temperatures.
- Nickel-Plated Brass: This is the industry workhorse. It offers fantastic mechanical strength, durability, and solid corrosion resistance. That makes it a go-to for a huge range of industrial environments, including places with oil and grease exposure.
- Stainless Steel (304 or 316L): When conditions get really tough, stainless steel is the undisputed champion. It delivers top-tier resistance to corrosion, chemicals, and high temperatures, making it a must-have for food processing, marine, and chemical plant applications.
The demand for these rugged components is clearly on the rise. Driven by industrialization and infrastructure projects, the global cable glands market was valued at around $2.4 billion in both 2022 and 2023. You can see more insights on this growing market and what's fueling it.
Demystifying Ingress Protection (IP) Ratings
The Ingress Protection (IP) rating is a non-negotiable spec that tells you how well a cable gland seals out solids (like dust) and liquids (like water). It's always two numbers: the first covers solids, and the second covers liquids.
A higher number means better protection. For example, an IP68 rating means the gland is completely dust-tight and can handle being continuously submerged in water under specific conditions.
Getting these ratings right is the key to making sure your connections are truly protected. For a more detailed look at how these ratings work for different gland designs, take a look at our guide on watertight cable glands.
Here’s a practical breakdown of the most common ratings you'll see:
- IP67: This gland is totally sealed against dust and can be submerged in water up to 1 meter deep for 30 minutes. It's a solid choice for equipment that might have to deal with temporary flooding.
- IP68: Offering an even higher level of water protection, an IP68-rated gland can handle continuous submersion at depths set by the manufacturer (usually more than 1 meter). This is the standard for any truly waterproof application.
- IP69K: This is the top of the line. It provides protection against high-pressure, high-temperature water jets. You'll find it's essential for equipment that gets frequent, intense washdowns, like in food and beverage processing plants.
Frequently Asked Questions About Cable Gland Sizing
Even with a detailed cable gland size chart in hand, questions always pop up for specific applications. Getting these details right is what prevents installation headaches, protects your system's integrity, and frankly, saves a ton of time on the job.
Here are straight answers to the most common questions our own engineers and technicians field every day. We'll cover the practical, real-world challenges to help you troubleshoot sizing issues and choose your components with total confidence.
What Happens If I Use a Gland at Its Clamping Range Edge?
Pushing a cable gland to the absolute minimum or maximum of its clamping range is a common temptation, but it’s a risky move. It’s a direct path to compromising the connection’s seal and overall reliability.
If you’re at the minimum limit, the sealing insert just can't compress enough to get a solid grip on the cable jacket. This almost guarantees a poor seal, which immediately voids the IP rating and offers very little in the way of strain relief.
On the other hand, using a gland at its maximum limit means you have to use excessive force just to tighten it down. This can easily damage the cable’s insulation or deform the gland's internal seal, creating a failure point waiting to happen.
The best practice is simple: always pick a gland where your cable's outer diameter sits comfortably within the middle third of the clamping range. This sweet spot ensures optimal compression for a durable, liquid-tight seal that will hold up for the long haul.
Can I Run Multiple Cables Through One Gland?
No. Standard cable glands are engineered with one job in mind: to seal perfectly around a single, round cable. Trying to stuff multiple cables through a standard gland is a critical error that will fail 100% of the time.
When you do this, you create unavoidable gaps between the individual cables and the sealing insert. This completely eliminates any Ingress Protection and also kills the strain relief function, since the gland can't grip any of the cables securely.
If you need to run several cables through a single entry point, you have to use the right tool for the job: a dedicated multi-hole or multi-conductor cable gland. These are designed with multiple, distinct openings in the seal to give you a secure, protected connection for each and every cable.
How Do I Convert Between PG and Metric Threads?
There isn't a direct mathematical formula to convert between Panzergewinde (PG) and Metric (M) threads. The reason is that their thread profiles and pitches are fundamentally different. Don't try to guess.
The only correct way to do this is with a PG-to-Metric conversion chart. These reference charts provide the closest Metric equivalent, based on the required clearance hole diameter and the gland's clamping range.
For example, a PG11 gland (which needs an 18.6 mm clearance hole) is often replaced by an M20 gland (which needs a 20.2 mm hole). In a retrofit, this means the hole must be enlarged slightly to accommodate the new Metric gland. Always measure the existing panel hole before you order a replacement to be certain of a proper fit.
Is a Locknut Always Necessary for Installation?
A locknut is a crucial part for securing a cable gland, but you don't need it in every single installation. Whether you use one or not depends entirely on the type of mounting hole in your enclosure.
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You must use a locknut when installing a gland into a smooth, unthreaded clearance hole. The locknut tightens from inside the enclosure, clamping the panel wall between itself and the gland body for a rock-solid mechanical connection.
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However, a locknut is not necessary if you're installing into a pre-tapped, threaded hole that perfectly matches the gland's threads (like an M25 gland into an M25 threaded hole). In this case, the gland screws directly into the equipment, creating its own secure fit. This is common on cast-metal enclosures and some types of machinery.
For a complete selection of industrial-grade cable glands, connectors, and automation components, visit Products for Automation. Our extensive catalog and expert support can help you find the perfect part for your MRO or OEM needs. Explore our full range at https://www.productsforautomation.com.