Drill pipe is a seamless steel tube with tool joints welded to each end and is an essential component of drilling operations across the oil and gas industry.
Every joint performs three jobs at once: it transmits rotary torque down to the drill bit, circulates drilling fluid through its bore and back up the annulus, and supports the weight of the drill string hanging below it.
Drill pipe comes in various sizes, and this guide covers drill pipe specifications for the common working range of 3½” through 6⅝” outside diameter under API Spec 5DP, the same range that global suppliers like Imex Canada stock from API-certified mills. A complete description reads like this: 5″ OD, 19.50 lb/ft, Grade S135, Range 2, IEU, NC50.
Key Takeaways
- Drill pipe from 3½” to 6⅝” OD is manufactured to API Spec 5DP, ensuring worldwide interchangeability.
- The 5″ 19.50 lb/ft pipe with an NC50 connection is the industry workhorse.
- Steel grades E75 through S135 are chosen based on well depth, torque, and environment.
- Range 2 joints (27 to 31 ft) and IEU upsets are the standard in this size range.
- The connection, not the tube, is usually the torsional weak point in a drill string.
- Imex Canada supplies fully documented API 5DP drill pipe across the entire range.
Governing Standards: API Spec 5DP and ISO 11961
API Specification 5DP is the primary industry standard for drill pipe. It defines the manufacturing process, testing, marking, and inspection requirements, from steel chemistry and finished dimensions to the weld between the tube and tool joint. API 5DP is harmonized with ISO 11961, so contractors anywhere in the world can order against either standard and receive the same product.
Compliance is what makes drill pipe interchangeable and safe: a 5″ NC50 machined in one country must make up cleanly with a 5″ NC50 machined anywhere else. On our projects, an undocumented pipe never goes in the hole.
Drill Pipe Sizes, Weights & Connections Chart (3½” – 6⅝”)
Size-by-Size Breakdown
The table below lists the most common drill pipe dimensions: outside diameter, nominal weight range, and the connection typically run on each size, reflecting what you will actually find in rental fleets and contractor inventories.
| Outside Diameter | Nominal Weight (lb/ft) | Typical Connection |
| 3½” | 13.30 to 15.50 | NC38 |
| 4″ | 14.00 to 16.60 | NC40 |
| 4½” | 16.60 to 20.00 | NC46 |
| 5″ | 19.50 to 25.60 | NC50 |
| 5½” | 21.90 to 24.70 | 5½ FH |
| 5⅞” | 23.40 | 5⅞ FH / XT57 |
| 6⅝” | 25.20 to 27.70 | 6⅝ FH |
A few field notes. The 5″ by 19.50 lb/ft pipe with an NC50 connection is the workhorse of land drilling worldwide and the easiest size to source.
At the small end, a 3 1/2″ pipe with an NC38 remains the standard for slim holes. The 5 7/8″ size gained ground in extended-reach drilling with better hydraulics than 5 1/2″ and none of the handling penalties of 6 5/8″. The XT57 beside 5⅞ FH is a proprietary double-shoulder connection for high-torque wells.
Smaller sizes such as 2 3/8″ and 2 7/8″ pipes serve workover and slimhole drilling operations but fall outside this chart. For a stiffer transition to the bottomhole assembly, heavy-weight drill pipe (HWDP) comes in these same ODs, with a much thicker wall that provides additional weight and rigidity above the drill collars.
Notes on Wall Thickness and Weight Variation
The weights in the chart are nominal; actual dimensions such as wall thickness and weight differ by pipe design. A heavier nominal weight in the same OD, such as 5″ 25.60 lb/ft versus 19.50 lb/ft, means a thicker wall and a smaller inside diameter.
A thicker wall brings more tensile and torsional capacity but also additional weight to hoist and higher pressure losses through the bore.
Mill paperwork also lists an adjusted weight, which adds the tool joint and upset material to the plain tube figure. And used pipe adds another layer: API RP 7G classifies it as Premium or Class 2 based on the remaining wall, so real capacity depends on inspection class.
Large-bore pipes deserve caution. On a 6⅝” drill pipe, the tool joint OD commonly runs 8″ or more and must pass freely inside the casing while leaving room for fluid flow, so always check the tool joint OD against the casing drift before running it.
Steel Grades and Mechanical Properties
Minimum Yield Strength by Grade
API 5DP defines four steel grades, each named for its minimum yield strength, the stress the steel carries before deforming permanently.
- Grade E75: 75,000 psi (517 MPa) minimum yield strength
- Grade X95: 95,000 psi (655 MPa) minimum yield strength
- Grade G105: 105,000 psi (724 MPa) minimum yield strength
- Grade S135: 135,000 psi (931 MPa) minimum yield strength
The letter is the grade family, and the number is the minimum yield in thousands of psi; some spec sheets write them as E-75, X-95, G-105, and S-135. Each grade also carries a minimum tensile strength requirement, the ultimate load the steel can withstand before it breaks.
How to Choose the Right Grade
Grade selection starts with well depth: the deeper the well, the more string weight hangs from the top joint. E75 handles shallow wells; engineers step up through X95 and G105 as depth increases, and S135 is the default for deep, extended-reach, and high-pressure wells because it carries the most load per pound of pipe.
Torque pushes the decision further. Horizontal wells generate high rotating torque and drag, and the superior strength of higher-grade pipe provides the margin for demanding drilling conditions, plus the overpull to work stuck pipe free.
The trade-off: higher-strength steels are more sensitive to hydrogen sulfide cracking and corrosion, so sour-service wells sometimes call for a lower grade or specially treated pipe. High-temperature environments deserve the same attention, since downhole heat reduces steel strength.
Grade selection balances depth, torque, and environment, not a race to the highest number.
Length Ranges Explained (R1, R2, R3)
API groups drill pipe into three ranges by joint length. Range 1 covers 18 to 22 ft (5.5 to 6.7 m) and suits rigs with limited mast height, workover units, and shallow drilling.
Range 2 covers 27 to 31 ft (8.2 to 9.4 m) and is by far the most common range in oil and gas drilling; most rig masts and handling tools are built around R2 joints. If a spec sheet does not state a range, R2 is almost always what is meant.
Range 3 covers 38 to 45 ft (11.6 to 13.7 m). R3 joints reduce the number of connections in the string, saving tripping time, but they need taller masts, so they belong on larger rigs, deep wells, and offshore operations.
Upset Types: IU, EU, and IEU
An upset is the thickened section forged at each end of the tube before the tool joint is welded on, strengthening the weld zone, the most highly stressed area of the pipe body.
Internal upset (IU) pipe thickens inward, keeping the OD flush for slim-hole work. External upset (EU) pipe thickens outward, leaving the bore at full diameter for better hydraulics and tool passage. Internal-external upset (IEU) pipe thickens in both directions, producing a stronger, balanced transition without choking the bore or ballooning the OD.
That is why IEU dominates this range: nearly every joint of standard 4 1/2″, 5″, and larger drill pipe in the field is IEU.
Tool Joints and Thread Connections
Connection Types by Size and Application
The tool joint connection is where drill pipe strings succeed or fail. Rotary-shouldered connectors come in various types and thread profiles, and most pipe in this range runs an NC (National Coarse) series connection.
NC38 pairs with 3½” pipe, NC40 with 4″, NC46 with 4½”, and NC50 with 5″. FH connections take over on larger pipe: 5½ FH, 5⅞ FH, and 6⅝ FH are sized for the heavier tool joints those larger pipe bodies require.
You will also hear IF and REG in the field. IF, or Internal Flush, is an older naming system, and many IF connections interchange dimensionally with their NC equivalents. REG connections appear mostly on bits and drill collars.
Connection choice follows outside diameter first, then application. Standard rotary-shouldered connections handle most vertical wells, while high-torque horizontal wells often move to double-shoulder designs, which can raise makeup torque capacity by 40 percent or more in the same OD.
The connection, not the tube, is usually the torsional weak point, and a connection suitable for the planned torque delivers optimal performance trip after trip.
Anatomy of the Tool Joint
Every joint has a pin on one end and a box on the other. The pin carries external threads, the box internal threads, and the pipe runs in the hole pin down. Both ends have a tapered thread and a shoulder that seals metal to metal at full makeup torque; the shoulder, not the threads, seals against drilling fluid pressure.
Between the tool joint and pipe body sits the weld area. Tool joints are forged separately, built thicker and harder than the tube so crews can make up and break the connection thousands of times, and then friction-welded on.
On used strings, the weld zone and last engaged thread are the two components we inspect most closely, since that is where fatigue cracks start, and a crack missed at inspection becomes costly downtime at the rig.
Many tool joints also carry hardbanding, a wear-resistant alloy applied in bands around the tool joint OD to extend durability while keeping casing wear low. On any string destined for a long lateral, we treat hardbanding as standard equipment.
How to Specify Drill Pipe: Key Selection Parameters
A complete drill pipe specification covers eight parameters. Leaving any of them open invites the wrong pipe to your location.
- Outside diameter (OD): the nominal tube size, 3½” to 6⅝” in this guide
- Nominal weight: in lb/ft or kg/m, which fixes the wall thickness class
- Steel grade: E75, X95, G105, or S135, chosen against depth and load
- Length range: R1, R2, or R3 to match the rig’s handling equipment
- Upset type: IU, EU, or IEU, with IEU the norm in this range
- Tool joint and thread connection: NC, FH, or double-shoulder, with tool joint OD and ID stated
- Inspection level: API RP 7G, or the stricter DS-1 and NS-1 programs
- Service condition: standard, sour service, offshore, or extended reach
The last two are the ones buyers skip most often. DS-1 Category 3 to 5 inspections catch defects that a basic API visual will not, and service condition drives everything from steel chemistry to thread compound. Specify all eight parameters up front, and the pipe that arrives will be the pipe the well needs.
Source Drill Pipe Built to API Spec 5DP from Imex Canada
Every specification in this guide only matters if the pipe at your location actually meets it. Imex Canada supplies API 5DP drill pipe in the full 3½” to 6⅝” range covered here, sourced from mills certified to API, ISO, and NS-1 standards and backed by more than 30 years of tubular supply experience.
From grade selection through logistics, our technical team in Calgary works with drilling contractors worldwide to deliver drill pipe that matches your string design, on time and fully documented.
Choosing the Right Drill Pipe for Your Well
Drill pipe selection comes down to matching the outside diameter to your hole size, the steel grade to your depth and torque loads, and the connection to the torque it must transmit. Get those right, and the drilling process runs without interruption.
If you are speccing a string now, request a quote, and our team will match pipe from inventory to your well design, or download the full specification sheet for the complete dimensional data behind every size in this guide.
Whether you are comparing steel grades, checking connection compatibility, or sourcing a full string of API 5DP drill pipe, the details matter. If you have any questions about drill pipe specifications, sizes, or which grade and connection fit your well design, just contact Imex Canada; we are happy to help.