How is tubing sized?

Tubing is sized by measuring the outer diameter because the outer diameter determines how the tubing will fit into fittings, brackets, and other components of a system. This measurement is essential for ensuring compatibility with other parts in piping systems, such as connectors and valves.

Measuring the outer diameter is particularly important because it influences the structural integrity of the tubing as well as its flow characteristics. Different applications require specific outer diameters to accommodate factors like pressure ratings and thermal expansion.

While the inner diameter is relevant for determining flow capacity, and material thickness can impact strength, the outer diameter is the primary measurement that standard sizing charts and fittings are based on in most applications. Length is also a necessary measurement but does not pertain to the tubing sizing itself; it is simply a measure of how much tubing is available for use.