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API Casing Specifications Reference Table

Complete API 5CT casing specifications for common grades and sizes. Includes burst pressure, collapse resistance, joint strength, wall thickness, weight, and drift diameter. Filter by grade or OD to find the data you need.

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Grade	OD (in)	Weight (lb/ft)	Wall (in)	ID (in)	Drift ID (in)	Burst (psi)	Collapse (psi)	Joint Str. (1000 lb)

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About API 5CT Casing Specifications

API Specification 5CT (ISO 11960) defines the technical requirements for steel pipes (casing and tubing) used in oil and gas well construction. The specification covers chemical composition, mechanical properties, and dimensional tolerances for casing grades ranging from H-40 through Q-125.

Burst pressure is the internal pressure rating calculated using the Barlow formula: P = 0.875 x (2 x Yp x t / OD), where Yp is minimum yield strength, t is wall thickness, and OD is outer diameter. The 0.875 factor accounts for the 12.5% API wall thickness tolerance.

Collapse pressure is the external pressure rating and depends on the D/t ratio. API Bulletin 5C3 defines four collapse regimes: yield strength collapse, plastic collapse, transition collapse, and elastic collapse. Thinner-walled pipe transitions to lower collapse formulas.

Joint strength represents the tensile load capacity of the threaded connection (STC, LTC, or BTC). Values shown here are for short-thread coupling (STC) connections unless noted. Long-thread (LTC) and buttress (BTC) connections have higher joint strengths.

Drift diameter is the minimum guaranteed internal passage. Per API, drift diameter = ID minus 1/8" for casing up to 9-5/8" OD, and ID minus 5/32" for larger sizes. All downhole tools must pass through the drift diameter.

The data in this table is compiled from API 5CT / API Bulletin 5C2 published specifications. Always verify against the latest edition for critical well design decisions.

Data sourced from API 5CT / API Bulletin 5C2 specifications. Values shown are for new pipe with short-thread couplings (STC). Actual performance may vary with pipe condition, temperature, and connection type. This reference is provided for educational and preliminary engineering purposes. Always verify against current API publications and manufacturer data for final well design. Not a substitute for professional engineering judgment.