API Reference Tables

API 5CT — Complete Casing & Tubing Specification Tables

Full API 5CT / ISO 11960 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.

→ Casing & Tubing Product Page → Grade Selector Tool → API 5L Line Pipe Tables

API 5CT Casing and Tubing Specifications

API 5CT / ISO 11960 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). Two PSL levels: PSL-1 standard, PSL-2 for gas wells, sour service, and HPHT.

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	35.82
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	62.56
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	96.73
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.

Use our interactive calculator to compute weight, burst pressure and collapse for any size.

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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	57.78	12.57
2⅞	73.02	9.35	9.45	—	13.91	14.06	—	8.64	54.74	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	23.07
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 (PSL-2)	Notes
H40	40	80	60	276	552	414	—	0.5	None required	✗ No	Not required	Conductor, shallow low-pressure wells
J55	55	80	75	379	552	517	—	0.5	None required	✗ No	Not required	Surface casing, low cost
K55	55	80	95	379	552	655	—	0.5	None required	✗ No	Not required	Higher tensile than J55
N80-1	80	110	100	552	758	689	—	0.5	N+T or Q+T	✗ No	Not required	Medium depth sweet wells
N80Q	80	110	100	552	758	689	—	0.5	Q+T only	✗ No	Not required	Q+T — tighter properties
R95	95	110	105	655	758	724	—	0.5	Q+T only	✗ No	Not required	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	Required PSL-2	Primary sour service grade. NACE limit 23 HRC
L80-3Cr	80	95	95	552	655	655	23 HRC	0.5	Q+T only	✗ No	Required PSL-2	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	Required PSL-2	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	Required PSL-2	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	Required	NACE limit 22 HRC. Higher strength sour
T95	95	110	105	655	758	724	25.4 HRC	0.5	Q+T only	✓ Yes	Required	NACE limit 22 HRC — hardness trap. Use PSL-2
P110	110	140	125	758	965	862	—	0.6	Q+T only	✗ No	Not required	Deep HPHT sweet wells only. NOT sour service
C110	110	120	115	758	828	793	29.0 HRC	0.7	Q+T only	✓ Yes	Required	Highest sour service strength. NACE limit 29.0 HRC. API 5CT 11th ed (Dec 2023)
Q125	125	150	135	862	1034	931	—	0.65	Q+T only	✗ No	Types 3&4 only	Ultra-deep HPHT sweet only. No HRC limit specified. API 5CT 11th ed (Dec 2023)

Critical — T95 Hardness Trap API 5CT allows 25.4 HRC for T95. NACE MR0175 requires maximum 22 HRC for sour service. Pipes that pass API inspection may still fail NACE qualification. Always specify the NACE hardness limit explicitly in your purchase order for T95 in sour service wells.

Sour Service Grade Selection

NACE MR0175/ISO 15156-2 defines sour service as any system where H₂S partial pressure exceeds 0.05 psia (0.0003 MPa). The correct grade escalation path for sour service is:

OCTG Sour Service Grade Selection by H₂S Partial Pressure (per NACE MR0175/ISO 15156-2)
H₂S Partial Pressure	Recommended Grade	Max Hardness (NACE)
< 0.05 psia	Any API 5CT grade	—
0.05–1.5 psia	L80-1 PSL-2	23 HRC
0.05–1.5 psia	T95 Type 1 PSL-2	22 HRC
1.5–15 psia	L80-1 or C110 PSL-2	23 HRC / 29.0 HRC
> 15 psia	C110 or CRA	29.0 HRC
High CO₂+H₂S	L80-13Cr or Super 13Cr	23 HRC

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?

API 5CT defines the following casing and tubing grades: H40, J55, K55, N80 (Type 1 and Q), R95, L80 (Type 1, 3Cr, 9Cr, 13Cr), C90, T95 (Type 1 and 2), C110, P110, and Q125 (Types 1-4). For sour service, the NACE MR0175 qualified grades are L80, C90, T95 Type 1, and C110.

What is the difference between API 5CT PSL-1 and PSL-2?

PSL-1 (Product Specification Level 1) is the baseline inspection level with standard mechanical testing and visual inspection. PSL-2 adds mandatory full-length non-destructive examination (NDE), Charpy impact testing, tighter dimensional tolerances, and per-joint traceability. PSL-2 is required for sour service, HPHT wells, and most international oil company (IOC) project specifications.

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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