Outside diameter in inches to nominal pipe size

Type a value in in OD to get it in NPS instantly.

Pipe size

From To

≈1NPS

That's about the same as a 1" gas line.

Convert the other way: NPS to in OD

What it means

How big is that pipe?

Steel pipe to ASME B36.10 / ISO 6708. The outside diameter is the same for every schedule; the wall, and so the bore, changes. Copper tube and PVC have their own sizes.

The math

How to convert in OD to NPS

Pipe sizes are a table: NPS 2 = DN 50 = 60.3 mm (2.375 in) OD, NPS 4 = DN 100 = 114.3 mm. From NPS 14 the OD equals the NPS in inches.

Example: 1.32 in OD = ≈1 NPS.

Every unit

That pipe in every system

Tables

in OD to NPS conversion table

in OD to NPS conversion table
in OD	NPS
0.405 in OD	1/8 NPS
0.54 in OD	1/4 NPS
0.675 in OD	3/8 NPS
0.84 in OD	1/2 NPS
1.05 in OD	3/4 NPS
1.32 in OD	≈1 NPS
1.66 in OD	1 1/4 NPS
1.9 in OD	1 1/2 NPS
2.38 in OD	≈2 NPS
2.88 in OD	≈2 1/2 NPS
3.5 in OD	3 NPS
4.5 in OD	4 NPS
5.56 in OD	≈5 NPS
6.62 in OD	≈6 NPS
8.63 in OD	≈8 NPS
10.8 in OD	≈10 NPS
12.8 in OD	≈12 1/8 NPS
14 in OD	14 NPS
16 in OD	16 NPS
18 in OD	18 NPS
20 in OD	20 NPS
24 in OD	24 NPS

NPS to in OD conversion table

NPS to in OD conversion table
NPS	in OD
1/8 NPS	0.405 in OD
1/4 NPS	0.54 in OD
3/8 NPS	0.675 in OD
1/2 NPS	0.84 in OD
3/4 NPS	1.05 in OD
1 NPS	1.315 in OD
1 1/4 NPS	1.66 in OD
1 1/2 NPS	1.9 in OD
2 NPS	2.375 in OD
2 1/2 NPS	2.875 in OD
3 NPS	3.5 in OD
4 NPS	4.5 in OD
5 NPS	5.563 in OD
6 NPS	6.625 in OD
8 NPS	8.625 in OD
10 NPS	10.75 in OD
12 NPS	12.75 in OD
14 NPS	14 in OD
16 NPS	16 in OD
18 NPS	18 in OD
20 NPS	20 in OD
24 NPS	24 in OD

Quick answers

How many NPS is 1 in OD?: 1 in OD is ≈3/4 NPS.
How many NPS is 10 in OD?: 10 in OD is ≈9 1/4 NPS.
How many NPS is 1.32 in OD?: 1.32 in OD is ≈1 NPS.

The units

About these units

Outside diameter in inches (in OD)

The actual outside diameter in inches.

Nominal pipe size (NPS)

The US nominal size in inches: ½, 1, 2…

Learn more about pipe units

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