Casing Size and Grade Chart

Oil and gas production begins by drilling a well in an oilfield.  Once a borehole is made, structural stability should be retained. To do this, a casing is inserted and pushed inside so that the wellstream will be sufficiently supported and protected and will not collapse or cave in. The gap between the wall of the well and the casing is cemented to fix the casing in place. Casing sizes are of different diameters and wall thickness. Made according to various specifications set by international organizations such as the American Petroleum Institute (API) and the  International Organization for Standardization (ISO), the casing size nominal diameter is equivalent to the theoretical diameter of the pipe and allowing for tolerance usually for an oversized pipe. Casing grades are based on set standards, or upon request, may be custom-made by particular manufacturers according to specifications provided by the customers.

Casing Size Importance

The inside diameter of the casing is vital as this dimension is a primary consideration in determining the tools that can pass through it. Likewise, it either determines the wall thickness or vice versa where the diameter is dependent on the required wall thickness.

Casing Grades Classification

Casing grades are classified according to metallurgical properties and mechanical properties such as yield strength, tensile strength, and hardness. Manufacturers adhering to standards produce casing grades that meet ISO 11960 or API Spec 5CT. These include yield strengths that range from 40,000 psi to 125,000 psi. As the grade increases, so does the strength of casing material.Casing grades that do not conform to specifications are special grades that require certain variations like resistance to sulfide stress cracking, high tensile strength, or high collapse strength.

Casing Size and Grade Chart

 

The Casing Size  and Grade Chart shows the following fields: The Outside Diameter(OD) is within ± 0.75% of the tolerance and must not be undersized. The Inside Diameter(ID) is designated as a drift diameter with a wall thickness equivalent to 87.5% of the nominal wall thickness and a tolerance of -12.5%.The Drift Diameter must pass through the casing within reasonable force exerted to the mandrel’s weight. Plain Ends(PE) refer to the threaded portion of the casing pipe without the coupling Threaded and Coupled(T&C) ends refer to the threaded and coupled portion of the casing Collar or coupling refers to joints of casing and enables the casing string to run. Grades classifications refer to (letter) chemical composition and (number) minimum yield strength.

Casing Size and Grade Chart Abbreviations:

• OD – Outside Diameter
• PE # / ft – Plain Ends number per feet
• T&C # / ft – Threaded and Coupled Ends number per feet
• STC – Short Thread and Coupled
• LTC – Long Thread and Coupled
• BTC – Buttress Thread Connection
• DWC – Drill With Casing
• API – American Petroleum Institute

Procuring the Right Casing Size and Grade for Your Drilling Operations

Selecting the optimal combination of casing size and grade requires balancing technical performance requirements with project economics, ensuring your casing program delivers reliable well integrity while maximizing capital efficiency. The charts above provide the essential specifications needed to evaluate casing options across the full range of API sizes and grades, but successful procurement also depends on understanding material availability, lead times for special orders, and the cost-benefit analysis of using premium used casing versus new pipe for specific well sections. Operators increasingly recognize that strategic casing selection—matching higher grades only where pressure and load conditions demand them, and using standard grades where adequate—can significantly reduce well construction costs without compromising safety or performance. Working with experienced suppliers who maintain diverse inventory and understand the nuances of casing specifications helps optimize your material selection for both immediate drilling needs and long-term well integrity.

Flowtech Energy stocks API 5CT certified casing in all standard sizes and grades, including both plain end and threaded-and-coupled configurations with STC, LTC, and BTC connections to match your specific well design requirements. Our inventory includes new premium casing for critical applications, inspected and certified used casing for cost-effective solutions, and access to mill-direct sourcing for large-volume projects or non-standard specifications. We understand that casing procurement involves more than just matching dimensional specifications—it requires verifying material certifications, coordinating delivery schedules with rig operations, and ensuring complete documentation for regulatory compliance and asset management. Our technical team provides engineering support to help you interpret grade requirements for specific downhole conditions, evaluate the suitability of used casing for redeployment, and structure procurement strategies that balance performance, availability, and budget constraints. If you need assistance selecting appropriate casing sizes and grades for your well program, sourcing certified material with complete mill test reports and traceability, or coordinating logistics for domestic or international delivery, contact Flowtech Energy at 1-877-645-6693. We deliver comprehensive procurement support—from initial specification review through final delivery—ensuring your drilling operations have the right casing at the right time to maintain schedule and budget targets while meeting all technical and regulatory requirements.

Go here if you are looking for the Casing Strength and Burst Pressure Chart.