When it comes to selecting the right fittings for your hydraulic or pneumatic systems, the choice between NPT (National Pipe Thread) and AN (Army-Navy) fittings can significantly impact the overall performance and reliability of your setup.
Today, we’ll explore the differences between NPT vs AN fittings, dive into the characteristics and applications of each, and offer guidance on how to choose the best option for your needs. If you have any questions about the article’s content, feel free to reach out to us.
What are NPT Fittings?

NPT fittings are widely used in fluid and gas systems. The NPT thread is a tapered thread, which provides a tight seal without the need for additional sealing elements. Here’s a breakdown of NPT fittings:
Structure of NPT Fittings:
- Tapered Threads: The threads on NPT fittings are tapered, meaning they get smaller as they go deeper into the fitting, which helps create a tighter seal when tightened.
- Sealing Mechanism: NPT fittings rely on thread deformation to form a seal, meaning that when the fitting is tightened, the threads push against each other to prevent leaks.
Common Sizes of NPT Fittings:
Size | Thread Pitch | Common Usage |
---|---|---|
1/4 NPT | 18 threads/inch | Plumbing, hydraulic systems |
1/8 NPT | 27 threads/inch | Small pipe connections, fuel lines |
3/8 NPT | 18 threads/inch | Fluid and gas transfer |
1/2 NPT | 14 threads/inch | Heavy-duty applications, compressors |
3/4 NPT | 14 threads/inch | Industrial and commercial use |
1 NPT | 11 threads/inch | Large pipelines, oil & gas systems |
Applications and Characteristics of NPT Fittings:
- Usage: NPT fittings are commonly used in plumbing, air, fuel lines, and other fluid transfer systems.
- Advantages: They are reliable, easy to install, and cost-effective.
- Disadvantages: Their sealing method can be compromised if not tightened correctly or if over-tightened.
What are AN Fittings?

AN fittings, which stand for Army-Navy fittings, are typically used in military and aerospace applications but have become a standard for high-performance automotive and fluid systems as well. The AN fitting is a straight thread fitting with a distinct design.
Structure of AN Fittings:
- Straight Threads: Unlike NPT, AN fittings have straight threads. The seal is made with a metal-to-metal connection, often with the help of a washer or O-ring.
- Locking Mechanism: AN fittings are designed to provide a strong connection with no risk of loosening under high-pressure conditions.
Common Sizes of AN Fittings:
Size | Thread Pitch | Common Usage |
---|---|---|
1/4 AN | 18 threads/inch | Fuel and oil systems, automotive |
3/8 AN | 18 threads/inch | Hydraulic systems, high-pressure applications |
1/2 AN | 20 threads/inch | Aerospace, heavy-duty applications |
10 AN | 24 threads/inch | High-performance racing, aviation |
Applications and Characteristics of AN Fittings:
- Usage: AN fittings are preferred in aerospace, motorsports, and other high-performance applications due to their durability and high-pressure tolerance.
- Advantages: They provide a leak-proof seal, even under extreme conditions, and are more resistant to corrosion compared to NPT fittings.
- Disadvantages: AN fittings require precise alignment and can be more expensive than NPT fittings.
NPT vs AN Fittings
Here’s a detailed breakdown of the key differences between NPT and AN fittings:
1. Thread Design:

- NPT: Tapered threads, which require tight fitting to create a seal.
- AN: Straight threads, which seal via a washer or O-ring.
2. Sealing Mechanism:
- NPT: Relies on thread deformation for sealing.
- AN: Seals with metal-to-metal contact and additional sealing elements like O-rings or washers.
3. Applications:
- NPT: Common in plumbing, general fluid transfer, and lower-pressure systems.
- AN: Used in high-performance and high-pressure systems like automotive, aerospace, and racing.
4. Compatibility:
- NPT: Not compatible with AN fittings due to the different thread designs and sealing methods.
- AN: AN fittings are typically not interchangeable with NPT fittings without the use of adapters.
5. Ease of Use:
- NPT: Easier to install, as they don’t require perfect alignment but may require thread sealant.
- AN: More precise installation, requiring alignment and the use of additional sealing elements.
6. Sizing System
- NPT: NPT fittings are sized based on a fractional inch system, which is related to the nominal pipe size. For example, a 1/2 NPT fitting has a specific thread size and outer diameter corresponding to the 1/2-inch nominal pipe size.
- AN: AN fittings use the dash number system, where the dash number represents the nominal inside diameter of the hose or tubing in 1/16-inch increments. This system can be a bit more confusing for those used to the traditional fractional inch sizing of NPT fittings.
In general, NPT and AN fittings are not interchangeable. Their different thread designs, sizing systems, and sealing mechanisms make it impossible to directly connect them without using an adapter. For example, you cannot simply screw a 1/4 NPT male fitting into a -4 AN female fitting.
If you need to connect a system with NPT fittings to one with AN fittings, you must use an appropriate adapter, such as as an an to npt adapter fitting or an npt to a fitting.
How to Choose Between NPT and AN Fittings

Choosing between NPT and AN fittings depends on the application and the specific requirements of your system.
Step 1: Determine the Application
The first step in choosing between NPT and AN fittings is to clearly define the application. If you are working on a plumbing project in your home or an industrial plant, NPT fittings are likely the more appropriate choice due to their widespread use in plumbing systems. On the other hand, if you are modifying a high-performance car’s fuel or hydraulic system, AN fittings would be a better fit.
Step 2: Consider the Pressure Requirements
If the system will operate under high pressure, AN fittings are often a better option. Their 37 – degree flare design is specifically engineered to handle high-pressure situations. However, if the pressure is relatively low to moderate, NPT fittings can also be suitable, especially if they are properly sealed.
Step 3: Evaluate the Fluid Being Transferred
The type of fluid being transferred can also influence your choice. For example, if the fluid is corrosive, you may need to choose fittings made of corrosion-resistant materials. Both NPT and AN fittings are available in a variety of materials, but in some cases, the material options may be more limited for one type of fitting over the other.
Step 4: Look at the Available Space
AN fittings are known for their compact design, which can be an advantage in tight spaces. If you are working in an area with limited space, such as an automotive engine bay or a complex industrial machinery setup, AN fittings may be easier to install. NPT fittings, with their larger and more traditional pipe-fitting-like design, may require more space for installation and connection.
Step 5: Consider Cost and Availability
In some regions, one type of fitting may be more readily available than the other. Additionally, the cost can vary depending on the material, size, and brand. NPT fittings are generally more commonly available in hardware stores and are often more affordable, especially for standard plumbing-sized fittings. AN fittings, especially those in specialized sizes or made of high-end materials, can be more expensive.
5. Key Takeaways
- NPT fittings are suitable for lower-pressure systems and are easier to install but rely on thread deformation for sealing.
- AN fittings provide a more durable, high-performance solution and are ideal for high-pressure systems, though they require precise installation.
- Both fitting types are not directly interchangeable, and special adapters may be required for mixed systems.
NPT to AN Fittings
NPT (National Pipe Taper) and AN (Army-Navy) are two common types of fittings used in various applications, including hydraulic systems. While they serve a similar purpose – connecting components in fluid systems – they have distinct designs and are not directly interchangeable.
NPT fittings utilize a tapered thread that forms a seal as it’s tightened. This design is widely used in plumbing and general industrial applications. AN fittings, on the other hand, feature a flared tube end that seals against a mating surface within the fitting. This design is commonly found in high-pressure applications, particularly in automotive and aerospace industries.
To connect components with different fitting types, such as NPT and AN, special adapters are required. These adapters bridge the gap between the two systems, allowing for a secure and leak-free connection.
Conclusion
In conclusion, when deciding between NPT VS AN fittings, it’s important to evaluate the specific needs of your system, including pressure, fluid type, and compatibility. If you have any doubts or need customized fittings, don’t hesitate to contact us.
For more information or to access our product catalog, visit our homepage.
FAQs About NPT VS AN fittings
Will NPT thread into an?
No, NPT fittings will not directly thread into AN fittings. NPT has a tapered 60-degree thread, while AN fittings have a 37-degree flare design with straight threads mainly for attaching the flare-nut. The thread forms and sealing mechanisms are completely different.
To connect an NPT-threaded component to an AN – fitting system, you need to use an appropriate adapter, such as an AN to NPT fitting or a not to an fitting. For example, if you have a 1/4 NPT male fitting and want to connect it to a -4 AN female fitting, you cannot simply screw them together. You must use an adapter that is designed to bridge the difference in thread and fitting types.
Are JIC and NPT compatible?
JIC (Joint Industry Council) and NPT are not directly compatible. JIC fittings have a 37-degree flare connection similar to AN fittings but are sized differently. NPT fittings have a tapered thread design. The sizing systems and connection methods are distinct.
For example, a JIC – sized fitting will not match the thread or connection style of an NPT fitting. However, there are adapter fittings available that can be used to connect systems with JIC and NPT components. These adapters are designed to convert the connection from one type to the other, allowing for a connection between the two different fitting systems.
What does the an line stand for?
The “AN” in AN fittings stands for “Army – Navy.” This type of fitting was originally developed for use in military applications, specifically in the U.S. Army and Navy. Over time, its design, which offers high – pressure resistance and a reliable seal, made it popular in other industries, especially in the automotive and industrial hydraulic sectors.
The AN sizing system, based on the dash number representing the nominal inside diameter of the hose or tubing in 1/16 – inch increments, was also developed as part of this military – derived standard.
What is compatible with NPT?
NPT fittings are compatible with other NPT – threaded components. This includes pipes, valves, and other fittings that are manufactured to the NPT standard. For example, a 3/8 NPT male fitting can be screwed into a 3/8 NPT female fitting. Additionally, there are some specialty adapters available that can connect NPT fittings to other types of fittings.
For instance, there are adapters that can connect NPT fittings to metric – threaded fittings or to fittings with different types of connections like compression fittings. However, it’s important to note that when using adapters, you must ensure that the connection is properly sealed and rated for the application’s pressure and fluid requirements.
What thread is an?
AN fittings have straight threads. These threads are not used for creating a seal in the same way as NPT threads. Instead, the threads on AN fittings are mainly used for attaching the flare – nut. The seal in AN fittings is created by the 37 – degree flare on the male fitting mating with the seat in the female fitting, and the flare – nut is tightened onto the threads to secure the connection.
For example, in a -6 AN fitting, the straight threads on the male and female parts are used to attach the flare – nut, which compresses the flare to create a leak – free seal.
Where to buy fittings?
You can get fittings by custom – ordering from us. Our brand is Dingfeng, and we offer a full range of fittings. Whether you need NPT, AN, or any other type of fitting, we’ve got you covered. Just feel free to contact us at any time.
Can You Reuse an Fittings?
Reusing hydraulic fittings can be done under certain conditions, but it’s crucial to prioritize safety and functionality. Fittings hydraulic should be thoroughly inspected for signs of wear, corrosion, or damage. If any damage is found, the fitting should be replaced. Reusable fittings must be cleaned thoroughly to remove any debris or contaminants that could compromise the seal.