API Drill Pipe refers to heavy-duty, thick-walled hollow steel pipes that comply with the American Petroleum Institute's API 5DP specification.
It is the core component of the drill string, connecting surface drilling equipment (such as the top drive or rotary table) to the Bottom Hole Assembly (BHA). In the drilling world, it is often called the "backbone" of the operation.
From 2-3/8" to 6-5/8", we supply the full range of API 5DP drill pipe. Click here to start your inquiry with the experts.
API Drill Pipe Dimensional & Weight Chart
This table covers the most common Outside Diameters (OD), their nominal weights, and the standard tool joint connections associated with them.
| Pipe OD (inches) | Nominal Weight (lb/ft) | Wall Thickness (inches) | Inside Diameter (inches) | Standard Connection (NC/API) |
| 2-3/8" | 6.65 | 0.280 | 1.815 | NC26 (2-3/8" IF) |
| 2-7/8" | 10.40 | 0.362 | 2.151 | NC31 (2-7/8" IF) |
| 3-1/2" | 13.30 | 0.368 | 2.764 | NC38 (3-1/2" IF) |
| 3-1/2" | 15.50 | 0.449 | 2.602 | NC38 (3-1/2" IF) |
| 4" | 14.00 | 0.330 | 3.340 | NC40 (4" FH) |
| 4-1/2" | 16.60 | 0.337 | 3.826 | NC46 (4" IF) |
| 4-1/2" | 20.00 | 0.430 | 3.640 | NC46 (4" IF) |
| 5" | 19.50 | 0.362 | 4.276 | NC50 (4-1/2" IF) |
| 5" | 25.60 | 0.500 | 4.000 | NC50 (4-1/2" IF) |
| 5-1/2" | 21.90 | 0.361 | 4.778 | 5-1/2" FH |
| 6-5/8" | 25.20 | 0.330 | 5.965 | 6-5/8" FH |
| 6-5/8" | 27.70 | 0.362 | 5.901 | 6-5/8" FH |
API Length Ranges
Drill pipe is not sold in exact lengths but rather in "Ranges" defined by API.
Range 1 (R1): 18 to 22 feet (5.5 – 6.7 m) - Rarely used for standard drilling.
Range 2 (R2): 27 to 32 feet (8.2 – 9.8 m) - The global industry standard.
Range 3 (R3): 38 to 45 feet (11.5 – 13.7 m) - Used for deep offshore rigs to reduce connection time.
API Steel Grades (Mechanical Properties)
Steel grade determines the yield strength and tensile strength of the pipe. Higher grades are required for deeper and more complex wells.
| API Grade | Yield Strength (psi) | Tensile Strength (psi) | Typical Use |
| E-75 | 75,000 | 100,000 | Shallow to medium wells. |
| L-95 | 95,000 | 105,000 | Specific load requirements. |
| G-105 | 105,000 | 115,000 | Deep wells / High stress. |
| S-135 | 135,000 | 145,000 | Ultra-deep / Complex wells. |
Common Upset Types (Internal/External Thickening)
Because the tool joints are welded to the pipe, the ends of the pipe must be thickened (upset) for a strong weld.
IU (Internal Upset): Wall is thickened toward the inside.
EU (External Upset): Wall is thickened toward the outside.
IEU (Internal & External Upset): Both inside and outside are thickened. (The most common modern standard).
Main Functions of API Drill Pipe
Transmitting Torque and Power: It transmits rotational energy from surface equipment to the drill bit at the bottom, allowing the bit to cut through rock formations.
Circulating Drilling Fluid (Mud): The pipe is hollow, allowing drilling pumps to circulate mud down to the bit to cool it, clean the wellbore, and carry rock cuttings back to the surface.
Extending the Wellbore: By connecting individual joints of pipe (adding singles), the drill string lengthens, enabling the bit to reach depths of thousands of meters.
Supporting Loads: The drill pipe must support the immense weight of all downhole components hanging below it (drill pipe, drill collars, bit, etc.).
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FAQ
What is the difference between drill pipe and heavy weight drill pipe?
Heavy-weight drill pipe (HWDP) has a wall thickness 2 to 3 times greater than that of conventional drill pipe, and is used to mitigate stress concentration between the drill pipe and drill collars, while also serving as a partial replacement for drill collars. It is installed between the drill pipe and drill collars as a transition section, reducing fatigue failure and enhancing drill string stability.
How to identify drill pipe grade?
Drill pipe grade can be identified by permanent markings on the pipe body, which are typically clearly stamped on the drill pipe body and include grade designations such as E75, X95, G105, S135, etc.
