API Reference Tables

API 5CT — Complete Casing & Tubing Specification Tables

Full API 5CT 11th Edition specification data: casing and tubing dimensions (OD, wall, weight, ID, drift), and mechanical properties by grade (H40–Q125). Searchable and filterable. Data per API 5CT latest edition.

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API 5CT Casing and Tubing Specifications

API 5CT, 11th Edition (December 2023, with Errata 1 of May 2024), governs casing and tubing for oil and gas wells. Covers grades H40, J55, K55, N80, L80 (Type 1, 3Cr, 9Cr, 13Cr), R95, C90, T95, P110, C110, Q125 — yield strengths 276 MPa to 862 MPa (40 ksi to 125 ksi). The standard has no Product Specification Levels — supplementary requirements are ordered individually by Annex A number.

Use these tables to look up OD, wall thickness, drift diameter, collapse and burst pressure ratings, and grade mechanical properties. Filter by grade or OD to find the specification you need.

Table data verified 2026-07-01 — API 5CT 11th Edition (Dec 2023).

Showing 99 of 99 sizes

API 5CT Casing Pipe Dimensions — OD, Wall Thickness, Nominal Weight and Drift (API 5CT 11th Edition, December 2023, Table C.18)
OD (in)	OD (mm)	Nominal Wt (lb/ft)	Nominal Wt (kg/m)*	Wall (mm)	ID (mm)	Drift (mm)	Plain-end Wt (kg/m)
4½	114.3	9.50	14.38	5.21	103.88	100.70	14.02
4½	114.3	10.50	15.73	5.69	102.92	99.74	15.24
4½	114.3	11.60	17.38	6.35	101.60	98.42	16.91
4½	114.3	13.50	19.87	7.37	99.56	96.38	19.44
4½	114.3	15.10	22.69	8.56	97.18	94.00	22.32
5	127	11.50	17.19	5.59	115.82	112.64	16.74
5	127	13.00	19.69	6.43	114.14	110.96	19.12
5	127	15.00	22.69	7.52	111.96	108.78	22.16
5	127	18.00	27.19	9.19	108.62	105.44	26.70
5	127	21.40	32.13	11.10	104.80	101.62	31.73
5	127	23.20	34.76	12.14	102.72	99.54	34.39
5	127	24.10	36.15	12.70	101.60	98.42	35.80
5½	139.7	14.00	20.91	6.20	127.30	124.12	20.41
5½	139.7	15.50	23.48	6.98	125.74	122.56	22.85
5½	139.7	17.00	25.72	7.72	124.26	121.08	25.13
5½	139.7	20.00	30.05	9.17	121.36	118.18	29.52
5½	139.7	23.00	34.05	10.54	118.62	115.44	33.57
5½	139.7	26.80	40.15	12.70	114.30	111.12	39.78
5½	139.7	29.70	44.47	14.27	111.16	107.98	44.14
5½	139.7	32.60	48.74	15.88	107.94	104.76	48.49
5½	139.7	35.30	52.80	17.45	104.80	101.62	52.61
5½	139.7	38.00	56.82	19.05	101.60	98.42	56.68
5½	139.7	40.50	60.64	20.62	98.46	95.28	60.55
5½	139.7	43.10	64.41	22.22	95.26	92.08	64.38
6⅝	168.28	20.00	29.76	7.32	153.64	150.46	29.06
6⅝	168.28	24.00	35.72	8.94	150.40	147.22	35.13
6⅝	168.28	28.00	41.67	10.59	147.10	143.92	41.18
6⅝	168.28	32.00	47.62	12.06	144.16	140.98	46.46
7	177.8	17.00	25.60	5.87	166.06	162.88	24.89
7	177.8	20.00	29.91	6.91	163.98	160.80	29.12
7	177.8	23.00	34.67	8.05	161.70	158.52	33.70
7	177.8	26.00	39.14	9.19	159.42	156.24	38.21
7	177.8	29.00	43.60	10.36	157.08	153.90	42.78
7	177.8	32.00	47.92	11.51	154.78	151.60	47.20
7	177.8	35.00	52.09	12.65	152.50	149.32	51.52
7	177.8	38.00	56.10	13.72	150.36	147.18	55.52
7	177.8	42.70	63.84	15.88	146.04	142.86	63.41
7	177.8	46.40	69.35	17.45	142.90	139.72	69.01
7	177.8	50.10	74.85	19.05	139.70	136.52	74.58
7	177.8	53.60	80.21	20.62	136.56	133.38	79.93
7	177.8	57.10	85.42	22.22	133.36	130.18	85.25
7⅝	193.68	24.00	35.72	7.62	178.44	175.26	34.96
7⅝	193.68	26.40	39.29	8.33	177.02	173.84	38.08
7⅝	193.68	29.70	44.20	9.52	174.64	171.46	43.24
7⅝	193.68	33.70	50.15	10.92	171.84	168.66	49.22
7⅝	193.68	39.00	58.04	12.70	168.28	165.10	56.68
7⅝	193.68	42.80	63.69	14.27	165.14	161.96	63.14
7⅝	193.68	45.30	67.41	15.11	163.46	160.28	66.54
7⅝	193.68	47.10	70.09	15.88	161.92	158.74	69.63
7⅝	193.68	51.20	76.19	17.45	158.78	155.60	75.84
7⅝	193.68	55.30	82.30	19.05	155.58	152.40	82.04
7¾	196.85	46.10	68.60	15.11	166.63	163.45	67.72
8⅝	219.08	24.00	35.72	6.71	205.66	202.48	35.14
8⅝	219.08	28.00	41.67	7.72	203.64	200.46	40.24
8⅝	219.08	32.00	47.62	8.94	201.20	198.02	46.33
8⅝	219.08	36.00	53.57	10.16	198.76	195.58	52.35
8⅝	219.08	40.00	59.53	11.43	196.22	193.04	58.53
8⅝	219.08	44.00	65.48	12.70	193.68	190.50	64.64
8⅝	219.08	49.00	72.92	14.15	190.78	187.60	71.51
9⅝	244.48	32.30	48.07	7.92	228.60	224.66	46.20
9⅝	244.48	36.00	53.57	8.94	226.60	222.63	51.93
9⅝	244.48	40.00	59.53	10.03	224.40	220.45	57.99
9⅝	244.48	43.50	64.74	11.05	222.40	218.41	63.61
9⅝	244.48	47.00	69.94	11.99	220.50	216.54	68.75
9⅝	244.48	53.50	79.62	13.84	216.80	212.83	78.72
9⅝	244.48	58.40	86.91	15.11	214.25	210.29	85.47
9⅝	244.48	59.40	88.40	15.47	213.50	209.58	87.37
9⅝	244.48	64.90	96.58	17.07	210.30	206.38	95.73
9⅝	244.48	70.30	104.62	18.64	207.20	203.23	103.82
9⅝	244.48	75.60	112.51	20.24	204.00	200.02	111.93
10¾	273.05	32.75	48.74	7.09	258.90	254.91	46.50
10¾	273.05	40.50	60.27	8.89	255.30	251.31	57.91
10¾	273.05	45.50	67.71	10.16	252.70	248.77	65.87
10¾	273.05	51.00	75.90	11.43	250.20	246.23	73.75
10¾	273.05	55.50	82.59	12.57	247.90	243.94	80.75
10¾	273.05	60.70	90.33	13.84	245.40	241.40	88.47
10¾	273.05	65.70	97.77	15.11	242.80	238.86	96.12
10¾	273.05	73.20	108.93	17.07	238.90	234.95	107.76
10¾	273.05	79.20	117.86	18.64	235.80	231.80	116.95
10¾	273.05	85.30	126.94	20.24	232.60	228.60	126.19
11¾	298.45	42.00	62.50	8.46	281.50	277.50	60.50
11¾	298.45	47.00	69.94	9.52	279.41	275.44	67.83
11¾	298.45	54.00	80.36	11.05	276.40	272.39	78.32
11¾	298.45	60.00	89.29	12.42	273.60	269.65	87.61
11¾	298.45	65.00	96.73	13.56	271.30	267.36	95.27
11¾	298.45	71.00	105.66	14.78	268.90	264.92	103.40
13⅜	339.72	48.00	71.43	8.38	322.96	318.99	68.48
13⅜	339.72	54.50	81.10	9.65	320.42	316.45	78.55
13⅜	339.72	61.00	90.78	10.92	317.88	313.91	88.55
13⅜	339.72	68.00	101.19	12.19	315.34	311.37	98.46
13⅜	339.72	72.00	107.15	13.06	313.60	309.63	105.21
16	406.4	65.00	96.73	9.53	387.40	382.57	93.27
16	406.4	75.00	111.61	11.13	384.10	379.37	108.49
16	406.4	84.00	125.01	12.57	381.30	376.48	122.09
16	406.4	109.00	162.21	16.66	373.10	368.30	160.13
18⅝	473.08	87.50	130.21	11.05	450.98	446.22	125.91
20	508	94.00	139.89	11.13	485.70	480.97	136.38
20	508	106.50	158.49	12.70	482.60	477.82	155.13
20	508	133.00	197.93	16.13	475.70	470.97	195.66

Source: API 5CT 11th edition (Dec 2023) Table C.18. Drift per Table C.20. *Nominal weight includes threads and couplings. Plain-end weight (Wpe) is pipe body only.

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Showing 45 of 45 sizes

API 5CT Tubing Dimensions — OD, Wall Thickness and Weight by Connection Type NU/EU/IJ (API 5CT 11th Edition, December 2023, Table C.19)
OD (in)	OD (mm)	Wt NU (lb/ft)	Wt EU (lb/ft)	Wt IJ (lb/ft)	Wt NU (kg/m)	Wt EU (kg/m)	Wt IJ (kg/m)	Wall (mm)	ID (mm)	Wpe (kg/m)
1.050	26.67	1.14	1.20	—	1.70	1.79	—	2.87	20.93	1.68
1.050	26.67	1.48	1.54	—	2.20	2.29	—	3.91	18.85	2.19
1.315	33.4	1.70	1.80	1.72	2.53	2.68	2.56	3.38	26.64	2.50
1.315	33.4	2.19	2.24	—	3.26	3.33	—	4.55	24.30	3.24
1.660	42.16	2.09	—	2.10	—	—	3.13	3.18	35.80	3.06
1.660	42.16	2.30	2.40	2.33	3.42	3.57	3.47	3.56	35.04	3.39
1.660	42.16	3.03	3.07	—	4.51	4.57	—	4.85	32.46	4.46
1.900	48.26	2.40	—	2.40	—	—	3.57	3.18	41.90	3.54
1.900	48.26	2.75	2.90	2.76	4.09	4.32	4.11	3.68	40.90	4.05
1.900	48.26	3.65	3.73	—	5.43	5.55	—	5.08	38.10	5.41
1.900	48.26	4.42	—	—	6.58	—	—	6.35	35.56	6.56
1.900	48.26	5.15	—	—	7.66	—	—	7.62	33.02	7.64
2.063	52.4	3.24	—	3.25	—	—	4.84	3.96	44.48	4.73
2.063	52.4	4.50	—	—	—	—	—	5.72	40.96	6.58
2⅜	60.32	4.00	—	—	5.95	—	—	4.24	51.84	5.86
2⅜	60.32	4.60	4.70	—	6.85	6.99	—	4.83	50.66	6.61
2⅜	60.32	5.80	5.95	—	8.63	8.85	—	6.45	47.42	8.57
2⅜	60.32	6.60	—	—	9.82	—	—	7.49	45.34	9.76
2⅜	60.32	7.35	7.45	—	10.94	11.09	—	8.53	43.26	10.89
2⅞	73.02	6.40	6.50	—	9.52	9.67	—	5.51	62.00	9.17
2⅞	73.02	7.80	7.90	—	11.61	11.76	—	7.01	59.00	11.41
2⅞	73.02	8.60	8.70	—	12.80	12.95	—	7.82	57.38	12.57
2⅞	73.02	9.35	9.45	—	13.91	14.06	—	8.64	55.74	13.72
2⅞	73.02	10.50	—	—	15.63	—	—	9.96	53.10	15.49
2⅞	73.02	11.50	—	—	17.11	—	—	11.18	50.66	17.05
3½	88.9	7.70	—	—	11.46	—	—	5.49	77.92	11.29
3½	88.9	9.20	9.30	—	13.69	13.84	—	6.45	76.00	13.12
3½	88.9	10.20	—	—	15.18	—	—	7.34	74.22	14.76
3½	88.9	12.70	12.95	—	18.90	19.27	—	9.52	69.86	18.64
3½	88.9	14.30	—	—	21.28	—	—	10.92	67.06	21.00
3½	88.9	15.50	—	—	23.07	—	—	12.09	64.72	22.91
3½	88.9	17.00	—	—	25.30	—	—	13.46	61.98	25.04
4	101.6	9.50	—	—	14.14	—	—	5.74	90.12	13.57
4	101.6	10.70	11.00	—	—	16.37	—	6.65	88.30	15.57
4	101.6	13.20	—	—	19.64	—	—	8.38	84.84	19.27
4	101.6	16.10	—	—	23.96	—	—	10.54	80.52	23.67
4	101.6	18.90	—	—	28.13	—	—	12.70	76.20	27.84
4	101.6	22.20	—	—	33.04	—	—	15.49	70.62	32.89
4½	114.3	12.60	12.75	—	18.75	18.97	—	6.88	100.54	18.23
4½	114.3	15.20	—	—	22.62	—	—	8.56	97.18	22.32
4½	114.3	17.00	—	—	25.30	—	—	9.65	95.00	24.90
4½	114.3	18.90	—	—	28.13	—	—	10.92	92.46	27.84
4½	114.3	21.50	—	—	32.00	—	—	12.70	88.90	31.82
4½	114.3	23.70	—	—	35.27	—	—	14.22	85.86	35.10
4½	114.3	26.10	—	—	38.84	—	—	16.00	82.30	38.79

Source: API 5CT 11th edition (Dec 2023) Table C.19. NU = Non-Upset, EU = External Upset, IJ = Integral Joint. "—" = connection type not listed for this size/weight. Wpe = plain-end weight (pipe body only).

API 5CT Grade Mechanical Properties — Yield Strength, Tensile Strength, Hardness and Sour Service Suitability for Grades H40–Q125 (API 5CT 11th Edition, December 2023, Tables C.1–C.2)
Grade	Min Yield (ksi)	Max Yield (ksi)	Min Tensile (ksi)	Min Yield (MPa)	Max Yield (MPa)	Min Tensile (MPa)	Max Hardness	Elong. Factor (e)	Heat Treatment	H₂S Service	Charpy	Notes
H40	40	80	60	276	552	414	—	0.5	None required	✗ No	None for pipe — 6.5.5	Conductor, shallow low-pressure wells
J55	55	80	75	379	552	517	—	0.5	None required	✗ No	None for pipe — 6.5.5	Surface casing, low cost
K55	55	80	95	379	552	655	—	0.5	None required	✗ No	None for pipe — 6.5.5	Higher tensile than J55
N80-1	80	110	100	552	758	689	—	0.5	N or N+T	✗ No	Optional — A.9 (SR 16)	Medium depth sweet wells
N80Q	80	110	100	552	758	689	—	0.5	Q+T only	✗ No	Optional — A.9 (SR 16)	Q+T — tighter properties
R95	95	110	105	655	758	724	—	0.5	Q+T only	✗ No	Optional — A.9 (SR 16)	Medium strength sweet service, alternative to T95 where sour not required
L80-1	80	95	95	552	655	655	23 HRC	0.5	Q+T only	✓ Yes	Optional — A.9 (SR 16)	Primary H₂S grade. API Table C.5 max mean 23.0 HRC / 241 HBW. No SSC test in API 5CT
L80-3Cr	80	95	95	552	655	655	23 HRC	0.5	Q+T only	✗ No	Optional — A.9 (SR 16)	2–3% Cr alloy for mild CO₂ in sweet wells. NOT sour service. API 5CT 11th ed (Dec 2023)
L80-9Cr	80	95	95	552	655	655	23 HRC	0.5	Q+T only	✗ No	Optional — A.9 (SR 16)	9% Cr alloy for CO₂ sweet wells. NOT sour/H₂S service. API 5CT 11th ed (Dec 2023)
L80-13Cr	80	95	95	552	655	655	23 HRC	0.5	Q+T only	✗ No	Optional — A.9 (SR 16)	13% Cr for high CO₂ sweet wells. NOT sour/H₂S service. API 5CT 11th ed (Dec 2023)
C90	90	105	100	621	724	689	25.4 HRC	0.5	Q+T only	✓ Yes	Optional — A.9 (SR 16)	API Table C.5 max mean 25.4 HRC / 255 HBW. SSC test per 6.14 / 9.10
T95	95	110	105	655	758	724	25.4 HRC	0.5	Q+T only	✓ Yes	Optional — A.9 (SR 16)	API Table C.5 max mean 25.4 HRC / 255 HBW. SSC test per 6.14 / 9.10; ceiling alterable by agreement under 6.7.1 c)
P110	110	140	125	758	965	862	—	0.6	Q+T only	✗ No	Optional — A.9 (SR 16)	Deep HPHT sweet wells only. NOT sour service
C110	110	120	115	758	828	793	29 HRC	0.7	Q+T only	✓ Yes	Mandatory — 6.5.5	Highest-strength H₂S grade. API Table C.5 max mean 29.0 HRC / 279 HBW. SSC test per 6.14 / 9.10
Q125	125	150	135	862	1034	931	—	0.65	Q+T only	✗ No	Mandatory — 6.5.5	Ultra-deep HPHT sweet only. No HRC limit specified. API 5CT 11th ed (Dec 2023)

Read the hardness figures as what they are The HRC values above are API 5CT Table C.5 limits, and footnote c makes them maximum mean hardness numbers, not per-indentation ceilings — 6.7.1 a) sets the single-indentation reject separately. API 5CT does not qualify any grade for sour service; its Caution in Section 1 points to NACE MR0175/ISO 15156, and the environmental limits for carbon and low-alloy steels are set in ISO 15156-2, a document with its own criteria that this page does not restate. If your project specification imposes a hardness limit, label it as a project requirement and keep it separate from the API acceptance criterion.

Sour Service Grade Selection

API 5CT does not decide sour service. Its Caution in Section 1 states that the standard "does not qualify the material for any specific sour service application" and points to NACE MR0175/ISO 15156 for material selection in H₂S environments; the partial-pressure envelope is set there, in ISO 15156-2 for carbon and low-alloy steels, not in API 5CT. What API 5CT does set is which grades carry an SSC test and what hardness each may reach:

What API 5CT Itself Specifies for the Sour-Related Grades
Grade	SSC test in API 5CT?	Max mean hardness (Table C.5)	Intended environment
L80 Type 1	No — 6.14 and 9.10 name C90, T95 and C110 only	23.0 HRC / 241 HBW	H₂S-bearing service
L80 3Cr / 9Cr / 13Cr	No	23.0 HRC / 241 HBW	CO₂ and chlorides — not sour grades
C90	Yes — 6.14, 9.10	25.4 HRC / 255 HBW	H₂S-bearing service
T95	Yes — 6.14, 9.10	25.4 HRC / 255 HBW	H₂S-bearing service
C110	Yes — 6.14, 9.10	29.0 HRC / 279 HBW	H₂S-bearing service
P110 / Q125	No	none specified	General service

Casing String Design Reference

Casing String Design Reference — String Type, OD Range, Common Grades and Primary Design Load
String Type	Typical OD Range	Common Grades	Primary Design Load
Conductor	16" – 30"	H40, J55	Structural, shallow
Surface	10-3/4" – 20"	J55, K55, N80	Kick containment, WOB
Intermediate	7" – 13-3/8"	N80, L80, P110	Burst from kick, tension
Production	4-1/2" – 9-5/8"	L80, T95, P110, C110	Collapse, burst, tension combined
Liner	4-1/2" – 7"	L80, T95, P110, C110	Same as production — no surface

Frequently Asked Questions

What is the drift diameter for API 5CT casing?

The drift diameter for API 5CT casing is the minimum internal diameter that a drift mandrel must pass through the full length of each pipe joint. It is smaller than the nominal ID — typically by 1.6mm (1/16 inch) for most sizes — confirming the bore is clear for tool and completion string passage.

What grades are available for API 5CT casing?

Clause 1.3 of the 11th Edition lists H40, J55, K55, N80 (all types), L80 (all types), C90, R95, T95, P110, C110 and Q125. Only two grades carry types: L80 has four (Type 1, 3Cr, 9Cr, 13Cr) and N80 has two (Type 1 and N80Q). T95 and Q125 have none. API 5CT does not qualify any grade for sour service — its Caution in Section 1 says so explicitly and points to NACE MR0175/ISO 15156. What the standard does specify is which grades carry a sulfide stress cracking test: clauses 6.14 and 9.10 are both titled for Grades C90, T95 and C110.

Does API 5CT have PSL-1 and PSL-2 levels?

No. The API 5CT 11th Edition contains no Product Specification Level concept — the phrase does not appear anywhere in the standard, and every "PSL" string in it is an end-finish code inside the dimension tables. PSL is an API 5L construct. In API 5CT the requirements a PSL is often assumed to bundle are controlled separately and ordered by name: nondestructive examination under clause 9.15 and A.3 (SR 2); Charpy impact testing under 6.5 and A.9 (SR 16); and traceability under 5.4.1, which is a purchaser-specified item in Table 2, or mandatory serialisation under 5.4.2 for Grades C90, T95, C110 and Q125.

What is the difference between API 5CT casing and tubing?

Casing is the larger-diameter pipe run to line the wellbore and isolate formation zones from the surface. Tubing is the smaller-diameter pipe run inside the casing through which hydrocarbons flow to surface. API 5CT covers both: casing ranges from 4½ inch to 20 inch OD; tubing from 1.050 inch to 4½ inch OD. Tubing is designed primarily for internal pressure and axial tension from production loads; casing is designed for external collapse, burst, and tensile loads from string weight.

What thread types are defined in API 5CT for casing and tubing?

API 5CT defines three standard threaded connections for casing: ST&C (Short Thread & Coupling), LT&C (Long Thread & Coupling), and BTC (Buttress Thread & Coupling). For tubing, the standard connections are EUE (External Upset End) and NUE (Non-Upset End). These API connections are the baseline. Premium threaded connections — such as VAM TOP, Tenaris TenarisHydril, and other proprietary designs — are covered by separate manufacturer specifications and provide higher gas-tightness and bending capacity for HPHT and deviated wells.

What hydrostatic test pressure is required for API 5CT casing?

API 5CT requires each casing length to be mill hydrostatic tested to a pressure calculated as P = 0.8 × (2 × Yp × t) / OD — 80% of the Barlow internal yield pressure — subject to a maximum of 69 MPa (10,000 psi) for standard grades. Sour-service grades (L80, C90, T95, C110) and Q125 have specific test pressure tables in API 5CT Annex E. The hydrostatic test confirms pipe body integrity but is not a design pressure; field operating pressures should be set with appropriate safety factors per the applicable well design code.

Related Technical Guides

→ API 5CT N80 Casing — Grades & Specifications → API 5CT L80 Casing — Sour Service Guide → API 5CT P110 Casing — Grades & HPHT → API 5CT T95 Casing — Sour Service → N80 vs L80 Casing Comparison → API 5CT vs NACE MR0175 Hardness Trap → Casing Connection Types — STC, LTC, BTC, Premium → Casing Design Basics — Collapse, Burst & Tension

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