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What is the difference between pipe and tube?
Short answer
Pipe is ordered by nominal pipe size and schedule, so its outside diameter is fixed and the bore changes with wall thickness. It carries fluids with standard fittings. Tube is ordered by exact outside diameter and wall thickness, with tighter tolerances, for heat exchangers, instruments, hydraulics and mechanical parts.
Pipe vs Tube at a glance
| Pipe | Tube | |
|---|---|---|
| Size basis | NPS / DN + schedule | Actual OD + wall (mm / BWG) |
| Tolerances | Standard | Tighter |
| Typical use | Process and utility piping | Heat exchangers, instrumentation, hydraulics |
| Joining | Butt-weld, flanged, threaded | Compression fittings, expanded, welded |
| Specs (stainless) | ASTM A312 | ASTM A213, A249, A269 |
Which should you choose?
There's no universal "winner": the right choice depends on service conditions, codes and cost. Share your conditions with us for a recommendation.
A quick example
"2-inch pipe" means NPS 2, which has an outside diameter of 60.3 mm whatever the schedule. "2-inch tube" means an outside diameter of 50.8 mm. Ordering by the wrong system is a common and costly mistake. See pipe schedules and NPS.
Specifications differ
Learn more
Related guides, comparisons and articles
Frequently asked questions
Can tube be used instead of pipe?
Only if the dimensions, tolerances and specification are accepted by the design. Fittings and flanges are dimensioned for pipe sizes.
How is tube wall thickness given?
In millimetres or in BWG gauge, as minimum or average wall depending on the specification.
What is the main difference between Pipe and Tube?
Pipe is ordered by nominal size and schedule to carry fluids with standard fittings. Tube is ordered by exact OD and wall thickness, with tighter tolerances, for heat exchangers, instruments and mechanical parts.
When should I choose Pipe?
Piping systems carrying fluids.
When should I choose Tube?
Heat transfer, instrumentation and precision parts.