News

OCTG Casing Pipe Size Chart

Keywords: casing size chart, OCTG casing pipe sizes, API 5CT casing dimensions, casing OD and weight

What is OCTG casing pipe?

OCTG casing pipe stands for "Oil Country Tubular Goods" and refers to a range of seamless rolled products such as drill pipe, casing and tubing used in drilling and producing oil and gas. Casing pipe is used to line the walls of a borehole to prevent collapse and to separate different layers of soil or rock. These pipes are made from various grades of steel and are designed to withstand the high pressures and corrosive environments encountered in oil and gas well operations.

API 5CT Casing Pipe Size Chart:

The size of OCTG casing pipe is specified by its outer diameter (OD) and wall thickness (WT), which are standardized according to American Petroleum Institute (API) standards. Common OCTG steel casing sizes range from 4-1/2 inches to 20 inches in outer diameter, with varying wall thicknesses to accommodate different well depths and pressure requirements.

How to use this size chart:

● Select casing size based on well depth and formation pressure — deeper wells require thicker walls
● Check steel grade compatibility — J55 casing for shallow wells, N80/P110 casing for deeper sections
● Verify clearance between casing, tubing, and drill string

Below is a standard oil and gas well casing size table, including outer diameter, wall thickness, weight, and coupling data. You can obtain detailed information from the table below.

Labels		Outside diameter	Nominal diameter	Wall thickness	Inside	Drift	Calculated mass C
					diameter	diameter	Plain End	Mass gain or loss due to end finishing (lb)
					diameter			Round thread		Buttress thread
1	2	OD (in)	lb/ft	WT (in)	ID (in)	in	lb/ft	Short	Long	RC	SCC
1	2	3	4	5	6	7	8	9	10	11	12
4 1/2	9.5	4.5	9.5	0.205	4.09	3.965	9.41	4.2
4 1/2	10.5	4.5	10.5	0.224	4.052	3.927	10.24	3.8		5	2.56
4 1/2	11.6	4.5	11.6	0.25	4	3.875	11.36	3.4	3.8	4.6	2.16
4 1/2	13.5	4.5	13.5	0.29	3.92	3.795	13.05		3.2	4	1.56
4 1/2	15.1	4.5	15.1	0.337	3.826	3.701	15		2.8	3.2	0.76
5	11.5	5	11.5	0.22	4.56	4.435	11.24	5.4
5	13	5	13	0.253	4.494	4.369	12.84	4.8	5.8	6.6	2.42
5	15	5	15	0.296	4.408	4.283	14.88	4.2	5.2	5.8	1.62
5	18	5	18	0.362	4.276	4.151	17.95		4.2	4.4	0.22
5	21.4	5	21.4	0.437	4.126	4.001	21.32		2.95	2.46	-1.72
5	23.2	5	23.2	0.478	4.044	3.919	23.11		2.3	2.05	-2.09
5	24.1	5	24.1	0.5	4	3.875	24.05		1.95	1.24	-2.94
5 1/2	14	5.5	14	0.244	5.015	4.887	13.71	5.4
5 1/2	15.5	5.5	15.5	0.275	4.95	4.825	15.36	4.8	5.8	6.4	2.1
5 1/2	17	5.5	17	0.304	4.892	4.767	16.89	4.4	5.4	5.8	1.5
5 1/2	20	5.5	20	0.361	4.778	4.653	19.83		4.4	4.6	0.3
5 1/2	23	5.5	23	0.415	4.67	4.545	22.56		3.2	3.4	0.9
5 1/2	26.8	5.5	26.8	0.5	4.5	4.375	26.72
5 1/2	29.7	5.5	29.7	0.562	4.376	4.251	29.67
5 1/2	32.6	5.5	32.6	0.625	4.25	4.125	32.57
5 1/2	35.3	5.5	35.3	0.687	4.126	4.001	35.35
5 1/2	38	5.5	38	0.75	4	3.875	38.08
5 1/2	40.5	5.5	40.5	0.812	3.876	3.751	40.69
5 1/2	43.1	5.5	43.1	0.875	3.75	3.625	43.26
6 5/8	20	6.625	20	0.288	6.049	5.924	19.51	11	13.6	14.4	2.38
6 5/8	24	6.625	24	0.352	5.921	5.796	23.6	9.6	12	12.6	0.58
6 5/8	28	6.625	28	0.417	5.791	5.666	27.67		10.2	10.6	-1.42
6 5/8	32	6.625	32	0.475	5.675	5.55	31.23		8.8	9	-3.02
7	17	7	17	0.231	6.538	6.413	16.72	10
7	20	7	20	0.272	6.456	6.331	19.56	9.4
7	23	7	23	0.317	6.366	6.25	22.65	8	10.4	11	1.6
7	23	7	23	0.317	6.366	6.241	22.65	8	10.4	11	1.6
7	26	7	26	0.362	6.276	6.151	25.69	7.2	9.4	9.6	0.2
7	29	7	29	0.408	6.184	6.059	28.75		8	8.2	1.2
7	32	7	32	0.453	6.094	6	31.7		6.6	6.8	2.6
7	32	7	32	0.453	6.094	5.969	31.7		6.6	6.8	2.6
7	35	7	35	0.498	6.004	5.879	34.61		5.6	5.6	3.8
7	38	7	38	0.54	5.92	5.795	37.29		4.4	4.2	5.2
7	42.7	7	42.7	0.625	5.75	5.625	42.59
7	46.4	7	46.4	0.687	5.625	5.5	46.36
7	50.1	7	50.1	0.75	5.5	5.375	50.11
7	53.6	7	53.6	0.812	5.376	5.251	53.71
7	57.1	7	57.1	0.875	5.25	5.125	57.29
7 5/8	24	7.625	24	0.3	7.025	6.9	23.49	15.8
7 5/8	26.4	7.625	26.4	0.328	6.969	6.844	25.59	15.2	19	20.6	6.21
7 5/8	29.7	7.625	29.7	0.375	6.875	6.75	29.06		17.4	18.8	4.41
7 5/8	33.7	7.625	33.7	0.43	6.765	6.64	33.07		15.8	17	2.61
7 5/8	39	7.625	39	0.5	6.625	6.5	38.08		13.6	14.6	0.21
7 5/8	42.8	7.625	42.8	0.562	6.501	6.376	42.43		12.01	11.39	-3.01
7 5/8	45.3	7.625	45.3	0.595	6.435	6.31	44.71		11.04	11.04	-3.36
7 5/8	47.1	7.625	47.1	0.625	6.375	6.25	46.77		10.16	9.23	-5.17
7 5/8	51.2	7.625	51.2	0.687	6.251	6.126	50.95
7 5/8	55.3	7.625	55.3	0.75	6.125	6	55.12
7 3/4	46.1	7.75	46.1	0.595	6.56	6.5	45.51
7 3/4	46.1	7.75	46.1	0.595	6.56	6.435	45.51
8 5/8	24	8.625	24	0.264	8.097	7.972	23.6	23.6
8 5/8	28	8.625	28	0.304	8.017	7.892	27.04	22.2
8 5/8	32	8.625	32	0.352	7.921	7.875	31.13	20.8	27.6	28.3	6.03
8 5/8	32	8.625	32	0.352	7.921	7.796	31.13	20.8	27.6	28.2	6.03
8 5/8	36	8.625	36	0.4	7.825	7.7	35.17	19.4	25.6	26.2	4.03
8 5/8	40	8.625	40	0.45	7.725	7.625	39.33		23.8	24.2	2.03
8 5/8	40	8.625	40	0.45	7.725	7.6	39.33		23.8	24.2	2.03
8 5/8	44	8.625	44	0.5	7.625	7.5	43.43		21.8	22.2	0.03
8 5/8	49	8.625	49	0.557	7.511	7.286	48.04		19.6	19.8	-2.37
9 5/8	32.3	9.625	32.3	0.312	9.001	8.845	31.06	24.4
9 5/8	36	9.625	36	0.352	8.921	8.876	34.89	23	32	31	6.48
9 5/8	40	9.625	40	0.395	8.835	8.75	38.97	21.4	30	29	4.48
9 5/8	40	9.625	40	0.395	8.835	8.679	38.97	21.4	30	29	4.48
9 5/8	43.5	9.625	43.5	0.435	8.755	8.599	42.73		28.2	27.2	2.68
9 5/8	47	9.625	47	0.472	8.681	8.525	46.18		26.6	25.6	1.08
9 5/8	53.5	9.625	53.5	0.545	8.535	8.5	52.9		23.4	22.4	-2.12
9 5/8	53.5	9.625	53.5	0.545	8.535	8.379	52.9		23.4	22.4	-2.12
9 5/8	58.4	9.625	58.4	0.595	8.435	8.375	57.44		21.5	20.13	-4.4
9 5/8	58.4	9.625	58.4	0.595	8.435	8.279	57.44		21.5	20.13	-4.4
9 5/8	59.4	9.625	59.4	0.609	8.407	8.251	58.7
9 5/8	64.9	9.625	64.9	0.672	8.281	8.125	64.32
9 5/8	70.3	9.625	70.3	0.734	8.157	8.001	69.76
9 5/8	75.6	9.625	75.6	0.797	8.031	7.875	75.21
10 3/4	32.75	10.75	32.75	0.279	10.192	10.036	31.23	29
10 3/4	40.5	10.75	40.5	0.35	10.05	9.894	38.91	26.4		34.4	7.21
10 3/4	45.5	10.75	45.5	0.4	9.95	9.875	44.26	24.4		31.8	4.61
10 3/4	45.5	10.75	45.5	0.4	9.95	9.794	44.26	24.4		31.8	4.61
10 3/4	51	10.75	51	0.45	9.85	9.694	49.55	22.6		29.4	2.21
10 3/4	55.5	10.75	55.5	0.495	9.76	9.625	54.26	20.8		27	-0.19
10 3/4	55.5	10.75	55.5	0.495	9.76	9.604	54.26	20.8		27	-0.19
10 3/4	60.7	10.75	60.7	0.545	9.66	9.504	59.45	18.8		24.4
10 3/4	65.7	10.75	65.7	0.595	9.56	9.404	64.59	16.8		22
10 3/4	73.2	10.75	73.2	0.672	9.406	9.25	72.4
10 3/4	79.2	10.75	79.2	0.734	9.282	9.126	78.59
10 3/4	85.3	10.75	85.3	0.797	9.156	9	84.8
11 3/4	42	11.75	42	0.333	11.084	11	40.64	29.6
11 3/4	42	11.75	42	0.333	11.084	10.928	40.64	29.6
11 3/4	47	11.75	47	0.375	11	10.844	45.6	27.6		35.8
11 3/4	54	11.75	54	0.435	10.88	10.724	52.62	25		32.4
11 3/4	60	11.75	60	0.489	10.772	10.625	58.87	22.6		29.6
11 3/4	60	11.75	60	0.489	10.772	10.616	58.87	22.6		29.6
11 3/4	65	11.75	65	0.534	10.682	10.625	64.03
11 3/4	65	11.75	65	0.534	10.682	10.625	64.03
11 3/4	71	11.75	71	0.582	10.586	10.43	69.48
13 3/8	48	13.375	48	0.33	12.715	12.559	46.02	33.2
13 3/8	54.5	13.375	54.5	0.38	12.615	12.459	52.79	30.8		40.2
13 3/8	61	13.375	61	0.43	12.515	12.359	59.5	28.4		36.8
13 3/8	68	13.375	68	0.48	12.415	12.259	66.17	25.8		33.6
13 3/8	72	13.375	72	0.514	12.347	12.25	70.67	24.2		31.6
13 3/8	72	13.375	72	0.514	12.347	12.191	70.67	24.2		31.6
16	65	16	65	0.375	15.25	15.062	62.64	42.6
16	75	16	75	0.438	15.124	14.936	72.86	38.2		45.6
16	84	16	84	0.495	15.01	14.822	82.05	34.2		39.6
16	109	16	109	0.656	14.688	14.5	107.6
18 5/8	87.5	18.625	87.5	0.435	17.755	17.567	84.59	73.6		86.4
20	94	20	94	0.438	19.124	18.936	91.59	47	61.2	54.8
20	106.5	20	106.5	0.5	19	18.812	104.23	41.6	54.8	48.4
20	133	20	133	0.635	18.73	18.542	131.45	30	40.6	35.2

Key Notes on Casing Size:

OD (Outside Diameter): Determines the size of the hole required for installation.

Weight (lbs/ft): Describes the linear weight of the casing, which varies based on wall thickness and steel grade.
Wall Thickness: Directly affects the casing's ability to withstand pressure and collapse forces.
ID (Inside Diameter): Influences the flow rate of the well.

How to Select the Right Casing Pipe Size?

Choosing the correct casing size is a critical engineering decision. The primary factors to consider are:

1. Well Depth and Pressure: Deeper wells encounter higher formation pressures and require casing with greater collapse and burst resistance, which typically means a larger outer diameter and/or thicker wall.
2. Formation Characteristics: The type of rock and soil being drilled through will determine the necessary casing strength and setting depth.
3. Completion Requirements: The planned method of production (e.g., whether you will use artificial lift) affects the required inner diameter (ID) to accommodate downhole equipment like pumps and packers.
4. Compatibility: The casing size must be compatible with the drill bit sizes used to create the borehole, as well as with the tubing and other equipment that will be run inside it.

Common Steel Grades and Their Applications

The steel grade of the casing determines its strength and resistance to corrosion. The choice of grade is closely tied to the casing size and the well's operating environment.

Steel Grade	Yield Strength (psi)	Typical Application & Notes
J55 / K55	55,000	Standard for shallow wells and surface casing where high strength is not required. Cost-effective.
N80	80,000	Versatile, most commonly used steel grade for medium-depth wells and standard production casing. (N80-Q is quenched & tempered for better properties).
L80	80,000	Same strength as N80 but with sour service (H₂S) resistance. Used in corrosive environments.
P110	110,000	High-strength steel for deep wells, high-pressure zones, and as production casing in demanding conditions.

Note: For a detailed breakdown of casing sizes and what each specification means, check out our guide: Specifications and Dimensions of Drilling Casing for Oil Fields.

Frequently Asked Questions:

Q1: What are the most common OCTG casing sizes?
The most frequently used sizes are 5-1/2 inch, 7 inch, and 9-5/8 inch, as they offer a good balance of strength and flow capacity for many wells.

Q2: How do I choose the right casing size for my well?
You need to consider well depth, expected downhole pressures, the geological formation, and the size of the production equipment. Always consult with a drilling engineer for a complete well design.

Q3: What does the “weight” (e.g., 23 lb/ft for 7-inch casing) mean in casing specifications?
It refers to the nominal linear weight of the casing in pounds per foot. It is a function of the casing's outer diameter, wall thickness, and steel grade.

Q4: Why can’t I use the same size casing for the whole well?
Because the loads (pressure, collapse, tension) are highest near the bottom of the well, and decrease towards the surface. Engineers use a "casing string design" with varying wall thicknesses and grades to optimize safety and cost.

Q5: What is the difference between casing and tubing?
Casing is the large-diameter pipe cemented in the well to support the borehole. Tubing is the smaller pipe run inside the casing through which the oil or gas is produced to the surface.

About us:

Hunan Standard Steel Co., Ltd (HSCO) provides API 5CT casing, API 5DP drill pipe, and couplings in a full range of specifications and steel grades. We offer both seamless and ERW casing, with optional premium connections.

Need a quote or technical advice? Contact our team: info@hu-steel.com

Further reading:

● Casing Pipe vs Drill Pipe: Every Driller Should Know

● Steel Grade of Casing Pipe

● API Casing Steel Grades: J55, N80, and P110 – How to Choose?

[Back]

Related information

2026-07-10Stainless Steel (SS) Pipe Dimensions Chart
2026-07-09Carbon Steel Square Tube Size Chart
2026-06-30OCTG Casing, Tubing, and Drill Pipe – What’s the Difference?
2026-06-24ERW vs. LSAW vs. SSAW: Key Differences & How to Choose
2026-06-18API Casing Steel Grades: J55, N80, and P110