What does pipe schedule mean?

Schedule is a wall-thickness series, not a measurement. For a given nominal pipe size the outside diameter never changes — a higher schedule number means a thicker wall growing inward, a smaller inside diameter and more weight per foot.

What does schedule 40 mean?

The most common wall series for steel pipe. For NPS 2 that is a 2.375 in outside diameter with a 0.154 in wall — about 3.66 lb/ft. Through NPS 10, schedule 40 and standard weight (STD) are the same wall; at NPS 12 and above they diverge.

Is NPS the same as the actual pipe diameter?

Not below NPS 14. A 2 in nominal pipe is actually 2.375 in outside; a 1/2 in pipe is 0.840 in. From NPS 14 up, nominal size and outside diameter match.

What is the difference between STD, XS and XXS?

Legacy weight classes: standard, extra strong and double extra strong. STD tracks schedule 40 through NPS 10, XS tracks schedule 80 through NPS 8, and XS wall holds at 0.500 in for larger sizes. XXS is its own heavy series and does not follow schedule 160.

What is the difference between pipe and HSS round tube?

Different products and specifications: pipe runs on NPS and schedule under its own standards, while round HSS is called out by actual outside diameter and decimal wall. The shapes overlap in use as columns and braces, but their designations and design values are not interchangeable.

Pipe schedule chart

Outside diameter, wall, inside diameter and weight per foot for steel pipe, NPS 1/8 through 24 — the schedules a shop actually meets: 5, 10, 40/STD, 80/XS, 160 and XXS. The OD never changes with schedule; the wall grows inward.

Pipe schedule lookup

Nominal pipe size (NPS)Schedule

Outside dia

2.375"

Wall

0.154"

Inside dia

2.067"

Weight

3.66 lb/ft

Plain-end weight at 10.69 × (OD − t) × t. Dimensional facts for estimating and orientation — pressure design belongs to the engineer of record.

The full chart

Plain-end weights at 10.69 × (OD − t) × t. The B36.10 matrix extends beyond these schedules — this covers the common series.

NPS	Schedule	OD (in)	Wall (in)	ID (in)	lb/ft
1/8"	40 / STD	0.405	0.068	0.269	0.24
	80 / XS	0.405	0.095	0.215	0.31
1/4"	40 / STD	0.540	0.088	0.364	0.43
	80 / XS	0.540	0.119	0.302	0.54
3/8"	40 / STD	0.675	0.091	0.493	0.57
	80 / XS	0.675	0.126	0.423	0.74
1/2"	5	0.840	0.065	0.710	0.54
	10	0.840	0.083	0.674	0.67
	40 / STD	0.840	0.109	0.622	0.85
	80 / XS	0.840	0.147	0.546	1.09
	160	0.840	0.188	0.464	1.31
	XXS	0.840	0.294	0.252	1.72
3/4"	5	1.050	0.065	0.920	0.68
	10	1.050	0.083	0.884	0.86
	40 / STD	1.050	0.113	0.824	1.13
	80 / XS	1.050	0.154	0.742	1.48
	160	1.050	0.219	0.612	1.95
	XXS	1.050	0.308	0.434	2.44
1"	5	1.315	0.065	1.185	0.87
	10	1.315	0.109	1.097	1.41
	40 / STD	1.315	0.133	1.049	1.68
	80 / XS	1.315	0.179	0.957	2.17
	160	1.315	0.250	0.815	2.85
	XXS	1.315	0.358	0.599	3.66
1-1/4"	5	1.660	0.065	1.530	1.11
	10	1.660	0.109	1.442	1.81
	40 / STD	1.660	0.140	1.380	2.27
	80 / XS	1.660	0.191	1.278	3.00
	160	1.660	0.250	1.160	3.77
	XXS	1.660	0.382	0.896	5.22
1-1/2"	5	1.900	0.065	1.770	1.28
	10	1.900	0.109	1.682	2.09
	40 / STD	1.900	0.145	1.610	2.72
	80 / XS	1.900	0.200	1.500	3.63
	160	1.900	0.281	1.338	4.86
	XXS	1.900	0.400	1.100	6.41
2"	5	2.375	0.065	2.245	1.61
	10	2.375	0.109	2.157	2.64
	40 / STD	2.375	0.154	2.067	3.66
	80 / XS	2.375	0.218	1.939	5.03
	160	2.375	0.344	1.687	7.47
	XXS	2.375	0.436	1.503	9.04
2-1/2"	5	2.875	0.083	2.709	2.48
	10	2.875	0.120	2.635	3.53
	40 / STD	2.875	0.203	2.469	5.80
	80 / XS	2.875	0.276	2.323	7.67
	160	2.875	0.375	2.125	10.02
	XXS	2.875	0.552	1.771	13.71
3"	5	3.500	0.083	3.334	3.03
	10	3.500	0.120	3.260	4.34
	40 / STD	3.500	0.216	3.068	7.58
	80 / XS	3.500	0.300	2.900	10.26
	160	3.500	0.438	2.624	14.34
	XXS	3.500	0.600	2.300	18.60
3-1/2"	5	4.000	0.083	3.834	3.48
	10	4.000	0.120	3.760	4.98
	40 / STD	4.000	0.226	3.548	9.12
	80 / XS	4.000	0.318	3.364	12.52
4"	5	4.500	0.083	4.334	3.92
	10	4.500	0.120	4.260	5.62
	40 / STD	4.500	0.237	4.026	10.80
	80 / XS	4.500	0.337	3.826	15.00
	160	4.500	0.531	3.438	22.53
	XXS	4.500	0.674	3.152	27.57
5"	5	5.563	0.109	5.345	6.36
	10	5.563	0.134	5.295	7.78
	40 / STD	5.563	0.258	5.047	14.63
	80 / XS	5.563	0.375	4.813	20.80
	160	5.563	0.625	4.313	32.99
	XXS	5.563	0.750	4.063	38.59
6"	5	6.625	0.109	6.407	7.59
	10	6.625	0.134	6.357	9.30
	40 / STD	6.625	0.280	6.065	18.99
	80 / XS	6.625	0.432	5.761	28.60
	160	6.625	0.719	5.187	45.39
	XXS	6.625	0.864	4.897	53.21
8"	5	8.625	0.109	8.407	9.92
	10	8.625	0.148	8.329	13.41
	40 / STD	8.625	0.322	7.981	28.58
	80 / XS	8.625	0.500	7.625	43.43
	XXS	8.625	0.875	6.875	72.49
	160	8.625	0.906	6.813	74.76
10"	5	10.750	0.134	10.482	15.21
	10	10.750	0.165	10.420	18.67
	40 / STD	10.750	0.365	10.020	40.52
	XS	10.750	0.500	9.750	54.79
	80	10.750	0.594	9.562	64.49
	XXS	10.750	1.000	8.750	104.23
	160	10.750	1.125	8.500	115.75
12"	5	12.750	0.156	12.438	21.00
	10	12.750	0.180	12.390	24.19
	STD	12.750	0.375	12.000	49.61
	40	12.750	0.406	11.938	53.57
	XS	12.750	0.500	11.750	65.48
	80	12.750	0.688	11.374	88.71
	XXS	12.750	1.000	10.750	125.61
	160	12.750	1.312	10.126	160.42
14"	10	14.000	0.250	13.500	36.75
	STD	14.000	0.375	13.250	54.62
	40	14.000	0.438	13.124	63.50
	XS	14.000	0.500	13.000	72.16
	80	14.000	0.750	12.500	106.23
	160	14.000	1.406	11.188	189.29
16"	10	16.000	0.250	15.500	42.09
	STD	16.000	0.375	15.250	62.64
	40 / XS	16.000	0.500	15.000	82.85
	80	16.000	0.844	14.312	136.74
	160	16.000	1.594	12.812	245.48
18"	10	18.000	0.250	17.500	47.44
	STD	18.000	0.375	17.250	70.65
	XS	18.000	0.500	17.000	93.54
	40	18.000	0.562	16.876	104.76
	80	18.000	0.938	16.124	171.08
	160	18.000	1.781	14.438	308.79
20"	10	20.000	0.250	19.500	52.78
	STD	20.000	0.375	19.250	78.67
	XS	20.000	0.500	19.000	104.23
	40	20.000	0.594	18.812	123.23
	80	20.000	1.031	17.938	209.06
	160	20.000	1.969	16.062	379.53
24"	10	24.000	0.250	23.500	63.47
	STD	24.000	0.375	23.250	94.71
	XS	24.000	0.500	23.000	125.61
	40	24.000	0.688	22.624	171.45
	80	24.000	1.219	21.562	296.86
	160	24.000	2.344	19.312	542.64

STD and XS rows are folded into their matching numeric schedules where the walls coincide; above the divergence points they carry their own walls (XS holds 0.500" from NPS 10 up). Dimensional facts for estimating — pressure and service design belong to the engineer of record.

Common questions

What does pipe schedule mean?: Schedule is a wall-thickness series, not a measurement. For a given nominal pipe size the outside diameter never changes — a higher schedule number means a thicker wall growing inward, a smaller inside diameter and more weight per foot.
What does schedule 40 mean?: The most common wall series for steel pipe. For NPS 2 that is a 2.375 in outside diameter with a 0.154 in wall — about 3.66 lb/ft. Through NPS 10, schedule 40 and standard weight (STD) are the same wall; at NPS 12 and above they diverge.
Is NPS the same as the actual pipe diameter?: Not below NPS 14. A 2 in nominal pipe is actually 2.375 in outside; a 1/2 in pipe is 0.840 in. From NPS 14 up, nominal size and outside diameter match.
What is the difference between STD, XS and XXS?: Legacy weight classes: standard, extra strong and double extra strong. STD tracks schedule 40 through NPS 10, XS tracks schedule 80 through NPS 8, and XS wall holds at 0.500 in for larger sizes. XXS is its own heavy series and does not follow schedule 160.
What is the difference between pipe and HSS round tube?: Different products and specifications: pipe runs on NPS and schedule under its own standards, while round HSS is called out by actual outside diameter and decimal wall. The shapes overlap in use as columns and braces, but their designations and design values are not interchangeable.

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