Pipe VS Tube - What's The Difference

Most have heard these two terms and yet few truly know the difference. Though the words pipe and tube (or tubing) are used interchangeably, they have very unique differences.

Application

Generally speaking, tube refers to hollow sections, whether square, rectangle, round or oval, used primarily in structural applications. Or where a precise outside diameter (OD), such as medical equipment is required.

Piping on the other hand is used primarily in the transport or conveyance of gases or fluids. An application where flow, a measure of capacity is the most important metric to determine capacity. With pipe, there’s less of an emphasis on OD.

Sizing

When talking about pipe or tube size, there are two measurements, OD and wall thickness (also referred to as gauge) and pipe schedule.

Outside Diameter (OD)

Tube requires an exact OD. As a result, both its measured and stated OD are within a very tight tolerance.

The OD for pipe is a nominal pipe size (NPS), whose measured and stated OD will have greater variation than tube.

NOMINAL PIPE SIZE OUTSIDE DIAMETER (INCHES)
1/2" 0.84
3/4" 1.05
1" 1.315
1-1/4" 1.66
1-1/2" 1.9
2" 2.375
2-1/2" 2.875
3" 3.5
3-1/2" 4

Wall Thickness & Pipe Schedule

Both terms are measures of the difference between OD and ID (inside diameter), but they are not interchangeable.

Wall thickness is a reference for tube, measured in inches or by standard gauge (7 the heaviest, 22 the lightest). Pipe schedule is a term used for pipe.

For additional information, please see our pipe schedule chart.

GAUGE THICKNESS RANGE(INCHES) TYPICAL VALUE (INCHES)
22 0.025 through 0.029 0.028
20 0.031 through 0.035 0.035
19 0.038 through 0.042 0.042
18 0.044 through 0.049 0.049
17 0.053 through 0.058 0.058
16 0.060 through 0.065 0.065
15 0.066 through 0.074 0.072
14 0.075 through 0.085 0.083
13 0.087 through 0.097 0.095
12 0.101 through 0.111 0.109
11 0.112 through 0.122 0.12
10 0.126 through 0.136 0.134
9 0.140 through 0.150 0.148
8 0.157 through 0.167 0.165
7 0.175 through 0.185 0.18
NOMINAL PIPE SIZE OD SCH 5 SCH 10 SCH 40 SCH 80
1/2" 0.84 0.065 0.083 0.109 0.147
3/4" 1.05 0.065 0.083 0.113 0.154
1" 1.315 0.065 0.109 0.133 0.179
1-1/4" 1.66 0.065 0.109 0.14 0.191
1-1/2" 1.9 0.065 0.109 0.145 0.2
2" 2.375 0.083 0.109 0.154 0.218
2-1/2" 2.875 0.083 0.12 0.203 0.276
3" 3.5 0.083 0.12 0.216 0.3
3-1/2" 4 0.083 0.12 0.226 0.318
4" 4.5 0.083 0.12 0.237 0.337

Cost

Generally, tube is more expensive than pipe due to the higher manufacturing requirements needed to ensure a more precise OD as compared to a nominal OD for pipe.

How to Order

Tube is typically ordered by OD and wall thickness. Though you can order by (1) OD and ID or (2) ID and wall thickness.

Pipe is ordered by the nominal pipe size (NPS) and the schedule number. For additional information, please see our pipe schedule chart, or view the tables above for reference.

Tube vs. Pipe

Titan Fittings
Tube
  • Structural
  • Exact OD
Structural

Exact OD
OD
Tube is normally used for structural purposes and sizing is based on the exact outside diameter and wall thickness of the tubing.
Pipe
  • Vessel
  • Nominal OD
Vessel

Nominal OD
OD
Pipe is normally used to transport gases or fluids and sizing is based on the nominal outside diameter (NPS) and wall thickness.
NPS Nominal Pipe Size

Many believe that NPS refers to the ID on smaller pipes because of how the standard was originally defined.

The NPS OD was originally defined so that a pipe with a standardized OD and wall thickness typical of the period, would have a pipe ID that was approximately equal to the nomimanl size of the pipe.

For example, a 3" schedule 40 NPS has an outside diameter and wall thickness that roughly gives in an indisde diamater of 3".

Regardless of Wall Thickness

The Nominal OD of a Pipe Will Not Change