Steel Pipe vs Steel Tube: What's the Difference?
Steel pipe vs tube explained: how each is specified (NPS and schedule vs OD and wall), tolerances, standards, shapes, uses and why ordering the wrong one causes problems.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: Pipes are specified by nominal pipe size and schedule and are designed to carry fluids under pressure, so the internal diameter and pressure rating matter. Tubes are specified by actual outside dimensions and wall thickness and are used for structural and mechanical purposes, where precise outside dimensions and strength matter. Tubes can be round, square or rectangular; pipes are round.
"Pipe" and "tube" are often used interchangeably, but in steel supply they mean different things. Mixing them up leads to the wrong product arriving on site.
Specification
| Aspect | Pipe | Tube / hollow section |
|---|---|---|
| Size basis | Nominal pipe size (NPS/DN) | Actual outside dimensions |
| Wall | Schedule or weight class | Wall thickness in mm |
| Shape | Round | Round, square, rectangular, oval |
| Key property | Pressure and flow | Strength, dimensions |
| Typical standards | ASTM A53, A106, API 5L, EN 10255 | EN 10219, EN 10210, ASTM A500, A513 |
Example of confusion
A buyer orders "50 mm pipe" for a handrail. Is that DN 50 (OD 60.3 mm) or a tube with 50 mm OD? Fittings and brackets designed for one will not fit the other. Always state OD and wall thickness in mm.
Typical uses
Pipes: water, fire fighting, oil and gas, steam, process piping, piling. Tubes/hollow sections: columns, trusses, frames, handrails, furniture, vehicle chassis, machinery, solar structures.
Tolerances
Tube standards for structural and mechanical uses often control outside dimensions, straightness and corner radii more tightly. Pipe standards focus on wall thickness, pressure testing and weld integrity.
Which to order
- Carrying fluids under pressure → pipe to the piping specification
- Structural member → hollow section to EN 10219/10210 or ASTM A500
- Precision mechanical part → mechanical tube (e.g. ASTM A513)
See SHS, RHS and CHS guide, pipe schedule chart, our steel pipes and hollow sections.