BSP VS NPT Threads:What are the Differences?

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In the field of hydraulic fittings and piping, two threads are international standards: the British Standard Pipe Thread (BSP) and the National Tapered Pipe Thread (NPT). These two thread systems have become the cornerstone of modern hydraulic applications and each has unique characteristics and areas of application. This article details all about BSP threads as well as NPT threads, so if you want to know more, please continue reading!

A Brief Historical Background

The evolution of BSP and NPT threads dates back to the Industrial Revolution when standardization became essential. The 55-degree angle of the BSP thread and the 60-degree angle characteristic of the NPT thread were developed by British engineer Joseph Whitworth and American engineer William Sellers, respectively.

The design developed by Sir Joseph Whitworth in the mid-19th century laid the foundation for the English line, known as the Whitworth line, which became the standard line in England and later spread to other European countries and Australia. The shape of the Whitworth line was revolutionary at the time, providing a uniform method of cutting and measuring lines. This innovation marked a major advance in engineering, making threaded connections more precise and consistent. The Whitworth system introduced the concept of standardized thread angles (specifically 55 degrees) and standardized thread pitches. This standardization facilitated the mass production of threaded parts and contributed to the rapid industrialization of the 19th century.

On the opposite shores of the Atlantic, William Sellers pioneered the introduction of the 60-degree thread angle, forming the foundation for the NPT (National Pipe Thread) standard. Recognized for its efficiency and ease of manufacture, Sellers’ design was swiftly adopted as the American standard. This innovation was more than a technical achievement; it marked a turning point in American engineering. By setting a precedent for threaded connections across diverse industries, Sellers’ 60-degree thread angle became synonymous with quality and precision. It facilitated standardization and mass production, driving industrial growth and technological advancement in the United States, and continues to be a vital part of modern hydraulic systems.


Threaded connections serve as the vital backbone of hydraulic systems. From the energy pulsing through power plants to the intricate workings of manufacturing facilities, the selection between inch (BSP) or American (NPT) threads significantly influences efficiency, safety, and performance. The choice is not merely technical; it embodies engineering philosophies. The metal-to-metal contact of an NPT fitting offers a robust seal, while the rounded contours of a BSP thread provide unique sealing properties. For professionals across various industries, understanding the nuances of these systems is more than essential; it’s a critical skill that underpins the integrity and functionality of countless hydraulic applications.

BSP vs NPT banner

BSP Pipe Threads

British Standard Pipe (BSP) threads are a hallmark of quality and precision in the hydraulic industry. Based on ISO 228 and Whitworth standard threads, BSP threads are the go-to choice in European countries and Australia. Their unique design, characterized by a 55-degree thread angle, sets them apart from other thread types, reflecting a commitment to quality, reliability, and innovation.

Types of BSP Threads


BSPP (British Standard Pipe Parallel): With parallel threads, BSPP offers a reliable and versatile option for various applications. It’s commonly used in low-pressure applications where a tight seal is required.

Parallel threads can be called BSPP or GAS threads, abbreviated as “G“. They are threads designed for gases. The internal and external threads of a parallel thread are sealed with the help of an O-ring to prevent fluid leakage.

Topa fitting BSPP


BSPT (British Standard Pipe Taper): Similar to NPT but with a 55-degree angle, BSPT threads provide a unique solution for specific needs. The tapered design allows for a more secure fit, making it suitable for high-pressure applications.

BSPT male threads are R series threads, while the female threads are called Rc series threads. They form a metal-to-metal seal when sealing and do not require the use of O-rings, although sealants are sometimes required.

BSPT Topa fitting


  ●Pitch: BSP threads are known for their distinct thread pitch, setting them apart from NPT threads. The specific pitch ensures a consistent fit across various fittings and applications.

  ●Angle: The 55-degree angle of BSP threads is a defining feature, contributing to their unique sealing properties. This angle provides a more gradual engagement between male and female threads, reducing the risk of over-tightening.

  ●Shape: Unlike the pointed peaks and valleys of NPT threads, BSP threads are rounded, offering a different sealing mechanism. This rounded design minimizes wear and tear, prolonging the lifespan of the connection.


  ●Adaptability: BSP threads are celebrated for their adaptability, suitable for a wide range of applications, from plumbing to industrial machinery.

  ●Efficiency: The unique design of BSP threads ensures a secure and leak-proof connection, enhancing the overall efficiency of the system.

  ●Compatibility: Understanding their compatibility is crucial, as mismatches with NPT threads can lead to leakage or failure under pressure. Careful selection and alignment are essential to prevent potential issues.


British Standard Pipe (BSP) threads are renowned for their precision and dependability, yet they come with certain limitations that might be relevant in particular scenarios:

  ●Potential Leakage: The characteristic rounded peaks and valleys of BSP threads can be both a strength and a weakness. While they offer unique sealing properties, if not correctly sealed, they might not provide a robust metal-to-metal contact. This could lead to potential leakage, a concern, especially in applications involving high pressure.

  ●Limited Availability in Certain Regions: While BSP threads are standard in many parts of the world, they may be less common in areas where NPT threads prevail, such as the United States and Canada. This limited availability might lead to delays in procurement or an increase in costs, affecting project timelines and budgets.


  ●Manufacturing: In manufacturing facilities, BSP threads are a preferred choice for professionals seeking precision and reliability. Their adaptability makes them suitable for various machinery and equipment.

  ●Oil and Gas: BSP threads are widely used in the oil and gas industry, where high-pressure applications demand secure and reliable connections.

  ●Automotive: In the automotive sector, BSP threads are used in fuel lines, hydraulic systems, and other critical components, ensuring optimal performance and safety.

  ●Construction: In construction equipment, BSP threads provide robust connections that can withstand the rigors of heavy-duty use.

NPT Pipe Threads

National Pipe Threads (NPT) are synonymous with quality and precision in the U.S. and Canada, and with a 60-degree angular taper, NPT threads have become the preferred choice for pressure calibration systems in North America. The standard has been a cornerstone of the hydraulic industry, reflecting a commitment to innovation and excellence.

Types of NPT Threads


NPT (National Pipe Taper Thread)threads have a 60-degree thread angle and are tapered threads designed to form a tight seal for a variety of applications. The taper of the threads provides a stronger fit and is suitable for high-pressure applications. However, NPT threads typically require sealing compound or PTFE tape to ensure a leak-proof connection. They are commonly used in plumbing, industrial manufacturing, and oil and gas exploration.

NPT threads also have a derivative thread, NPTF threads. NPTF threads improve the thread standard and sealing than NPT threads. Therefore, NPTF provides a stronger seal and a more secure connection.

NPT Fitting drawing Topa


Unlike NPT, NPS(National Pipe Straight Thread)threads are straight rather than tapered. This design is not as self-sealing as NPT threads, so a gasket or washer is usually required for sealing. nps threads are typically used in applications that do not require a leak-proof seal, such as some low-pressure applications or where a jam nut is used to secure the connection. The straight thread design makes them more suitable for connections that require frequent disassembly and reassembly with less risk of thread wear.

NPS fitting drawing Topa


  Pitch: NPT threads are known for their specific thread pitch, distinct from BSP threads. This unique pitch ensures a consistent and secure fit across various applications.
  Angle: The 60-degree angle of NPT threads is a defining feature, contributing to their unique sealing properties. This angle allows for a more gradual engagement, reducing the risk of over-tightening.
  Shape: Unlike the rounded peaks and valleys of BSP threads, NPT threads are pointed, offering a metal-to-metal contact that ensures an excellent seal. This design enhances the connection’s durability and longevity.


  ●Readily available: NPT threads are readily available in a wide range of sizes and materials and are easily found in supplier inventories, making them a convenient choice for a variety of industries.

  ●Versatile: Suitable for a wide range of applications at different pressures, NPT threads are flexible and adaptable to meet a wide range of needs.

  ●Easy assembly: Metal-to-metal contact provides an excellent seal, making assembly simple and efficient, saving time and resources.


  ●Deformation: Relying on thread deformation for sealing limits its use in applications that require frequent disassembly, which may shorten its life.

  ●Potential Leakage: Improper alignment, over-tightening, or miss-sizing can lead to cracks and leaks, making NPT threads unsuitable for use in very high-pressure applications. Proper installation and maintenance are essential to minimize these risks.


  ●Industrial Manufacturing: NPT threads are widely used in manufacturing equipment where precision and reliability are critical. They are adaptable to a wide range of machinery and equipment.

  ●Oil and Gas Exploration: In the demanding environment of oil and gas exploration, NPT threads provide a robust connection that can withstand high pressures and harsh conditions.

  ●Automotive: NPT threads are vital in automotive manufacturing for fuel lines, hydraulic systems, and other critical components to ensure safety and performance.

  ●Construction: In construction equipment and large infrastructure projects, NPT threads provide a robust connection that can withstand heavy-duty use.


BSP and NPT threads differ in geographical usage, thread forms, angles, and pitches. While NPT threads are prevalent in North America, BSP threads are the standard across other regions. Their incompatibility emphasizes the importance of precise selection, as mismatches can lead to leakage or failure.

Regional Usage

BSP and NPT threads are more than just technical specifications; they represent regional preferences. NPT threads are common in the United States and Canada, while BSP threads are the dominant standard in the United Kingdom, Europe, Asia, Australia, and many other countries. This geographical difference emphasizes the importance of selecting the correct thread type for a particular market and application.

Thread forms and angles

The physical differences between inch and hexagonal threads are subtle and significant; NPT threads have pointed crests and valleys, whereas inch threads are rounded. In addition, NPT threads are angled at 60 degrees while BSP threads are angled at 55 degrees. These differences in shape and angle contribute to their unique sealing properties and applications. They also affect the compatibility and interchangeability of these threads and require careful consideration during design and assembly.

BSP vs NPT threads Topa

Thread Pitch Comparison

Another important difference between inch and American threads is the thread pitch. For many fractional pipe sizes, the thread pitch is different from NPT. The difference in pitch can lead to thread misalignment, fluid leaks, and even catastrophic failure under pressure. Understanding these nuances is critical for professionals in the hydraulics industry, as it helps in selecting the correct thread type for a particular application.

BSP size chart Topa
BSP thread size chart
NPT size chart Topa
NPT thread size chart

Incompatibilities and Implications

BSP and NPT threads are not interchangeable due to their different shapes, angles, and pitches. Attempting to screw NPT male threads into BSPP female threads can lead to problems such as leakage and failure. This incompatibility highlights the importance of expertise and precision in selecting and using the correct thread type. It also highlights the need for standardized practices and guidelines to ensure safety and performance.

Impact on industry practices

Comparisons between British and American threads are not limited to technical aspects; they also influence industry practices and standards. From manufacturing to maintenance, the choice between BSP and NPT threads affects the design, function and efficiency of hydraulic systems. It also affects component availability, supplier relationships and overall cost considerations.


For professionals in the hydraulics industry, it is critical to understand the uniqueness, compatibility and applications of NPT and BSP threads. Whether it’s the adaptability of the BSP thread or the efficiency of the NPT thread, these systems play a vital role in a variety of industries, from manufacturing to oil and gas exploration. They must be selected and utilized with expertise and precision to ensure optimal performance, safety, and reliability.

For more detailed information on BSP and NPT hydraulic fittings and adapters or to make an inquiry, you are welcome to contact Topa and we will address your concerns.