Dimension table for hose and couplings

When selecting hoses and fittings, it is important to ensure that the dimensions, thread types, and connection standards are compatible. An incorrect combination can lead to leaks, pressure losses, damage to components, or downtime.

On this page, you'll find two tables. The first helps you compare common size designations such as inches, DN, millimeters, and size codes. The second shows which threads, pipe fittings, and coupling standards are typically used with different hose sizes.

The tables are intended as a guide. Always check the product’s exact dimensions, connection standard, and technical specifications before selecting a hose or fitting.

How to Use the Tables

Start by identifying the hose's inner diameter or size designation. Use the first table to see how that dimension corresponds to inches, DN, and millimeters.

Once you have identified the hose size, you can move on to the second table. There, you can compare the hose size with different threads, pipe fittings, and coupling standards.

Keep in mind that the hose’s inch size and the thread’s inch size are not always the same. They refer to different parts of the connection and must therefore be checked separately.

Conversion Table for Hose Sizes

The first table shows the relationship between:

• hose size in inches
• size designation, such as -4, -6, and -8
• nominal diameter, DN
• equivalent measurement in millimeters

What does the table show?

• Tum is often used to indicate the inner diameter of the hose.
• Size designation, also known as dash size, is usually based on sixteenths of an inch. For example, -8 corresponds to eight sixteenths, which is 1/2 inch.
• DN stands for nominal diameter and is a standardized size designation. The DN value does not always correspond to an exact measured dimension in millimeters.
• Millimeter shows the mathematical or approximate equivalent of the inch dimension.

This table is primarily useful when you want to convert a hose size or compare different ways of specifying the same size.

Dimension Table for Hoses, Threads, and Fittings

The table lists the size designation and the hose's inner diameter, as well as the corresponding dimensions for, among others, R-thread/BSP, NPTF, JIC 37°, SAE 45°, DKL, DKO-L, DKS, DKO-S, DKM, and DKF.

What does the table for hoses and fittings show?

Clear the column Size designation or Slang ID and then follow the row to the right. There you'll see which threads, pipe fittings, and coupling sizes are typically used for that hose size.

For example, a hose with the size designation -8 and inner diameter 1/2 inch are available with a variety of connections, such as BSP, NPTF, JIC, SAE, and metric connections.

The table does not, therefore, show that the connections are interchangeable. It shows which dimensions correspond to each standard for a given hose size.

Frequently Asked Questions About Hose and Fitting Sizes

What do size designations like -4, -6, and -8 mean?

Size designations are usually based on sixteenths of an inch.

• -4 is equal to 4/16 of an inch, or 1/4 inch
• -6 is equal to 6/16 of an inch, which is 3/8 of an inch
• -8 is equal to 8/16 of an inch, or 1/2 inch
• -12 is equivalent to 12/16 of an inch, or 3/4 of an inch
• -16 is equivalent to 16/16 of an inch, or 1 inch

What does "Slang ID" mean?

Hose ID refers to the inner diameter of the hose. ID is an abbreviation of the English term inside diameter.

The inner diameter is usually used to specify the hose size and flow capacity.

What does DN stand for?

DN stands for nominal diameter. It is a standardized designation used to classify hoses, pipes, and fittings by size.

DN is not always the same as the precisely measured diameter in millimeters.

How do you measure the inner diameter of a hose?

Measure the hose’s inner diameter from inner edge to inner edge, preferably with a caliper. Avoid measuring the hose’s outer diameter, as it can vary depending on wall thickness and construction.

Is the hose's inch size the same as the thread's inch size?

No. A hose size in inches usually refers to the hose's inner diameter, while a thread size is a nominal designation within a specific thread standard.

For this reason, a 1/2-inch BSP thread, for example, does not have an outside diameter of exactly 1/2 inch.

What is the difference between BSP and NPT/NPTF?

BSP and NPT/NPTF are different thread standards. BSP is used primarily in Europe and typically has a thread angle of 55 degrees, while NPT and NPTF are used primarily in North America and have a thread angle of 60 degrees.

NPT and NPTF have the same basic thread profile, but NPTF has tighter tolerances and is designed to create a seal within the threaded joint itself. BSP and NPT/NPTF should not be combined without a designated adapter.

What is the difference between JIC 37° and SAE 45°?

The difference lies primarily in the angle of the sealing cone.

JIC uses 37 degrees, while SAE uses 45 degrees. The couplings may look similar, but they do not seal properly against each other and should therefore not be mixed.

What is the difference between pressure classes L and S?

L stands for "light series" and S for "heavy series.".

The heavy-duty series is typically used for higher pressures and often features heavier-gauge tubing and fittings. The same metric thread may be used in different series, which means that the tubing size and fitting type must also be checked.