Drill pipe is the primary structural and fluid-conducting component of the drill string in rotary drilling operations. Manufactured to API Specification 5DP, it must simultaneously transmit torque, carry axial loads (tension and compression), and conduct drilling fluid under high pressure — often in deviated or deep wells where loads are extreme and failure consequences are severe.
This reference covers the full technical specification for API 5DP drill pipe: grade classifications, standard OD sizes and wall thicknesses, weight per foot, tool joint dimensions, range lengths, and the selection criteria that govern grade and weight class decisions. ZC Steel Pipe manufactures drill pipe to API 5DP in all standard grades and sizes, with export experience across Africa, the Middle East, and South America.
CONTENTS
What Is Drill Pipe? Definition and Function
API 5DP Grade Classifications
Standard OD Sizes and Wall Thicknesses
Drill Pipe Weight Per Foot
Tool Joint Specifications
Range Lengths
Heavy Weight Drill Pipe (HWDP)
Grade Selection Guide
FAQ
1. What Is Drill Pipe? Definition and Function
Drill pipe forms the main body of the drill string — the rotating assembly that connects the surface rig equipment to the drill bit at the bottom of the wellbore. Each joint of drill pipe consists of a tube body with upset ends (thickened wall sections) to which tool joints are friction-welded. The tool joints — pin on one end, box on the other — provide the threaded connections that allow the string to be assembled and disassembled during tripping operations.
API 5DP — SPECIFICATION FOR DRILL PIPEAPI Specification 5DP is the governing standard for drill pipe used in oil and gas drilling. It covers material grades, mechanical properties (yield strength, tensile strength, hardness), dimensional requirements (OD tolerances, wall thickness, body straightness), and inspection criteria. The standard is maintained by the American Petroleum Institute and is recognized globally as the baseline quality requirement for drill pipe procurement.
During drilling, the drill string performs four simultaneous functions: it transmits rotary torque from the surface to the drill bit; it carries the tensile load of the entire string hanging in the wellbore; it conducts drilling fluid downward through the drill pipe bore to cool the bit and carry cuttings back to surface; and in directional wells, it transmits the weight-on-bit loads required to build inclination. Each of these functions imposes distinct mechanical demands, which is why grade selection is critical.
Field Note — Drill String ArchitectureStandard drill pipe is not used directly above the drill bit. The bottom-hole assembly (BHA) uses drill collars and heavy weight drill pipe (HWDP) as a transition zone to provide weight-on-bit and reduce fatigue at the critical transition point. Standard drill pipe sits above the HWDP. Engineers specifying drill pipe for a new well program should dimension the HWDP transition zone first before sizing the main string.
2. API 5DP Grade Classifications
API 5DP defines four standard drill pipe grades, each differentiated by minimum yield strength, tensile strength, and hardness. Grade selection is the primary lever controlling tensile capacity, torsional strength, and resistance to hydrogen-induced stress cracking (HISC) in sour service environments.
| Grade | Min. Yield Strength (psi) | Max. Yield Strength (psi) | Min. Tensile Strength (psi) | Max. Hardness (HRC) | Typical Application |
| E75 | 75,000 | 105,000 | 100,000 | — | Shallow to medium wells, low H₂S exposure |
| X95 | 95,000 | 125,000 | 105,000 | — | Medium-depth wells, moderate torque requirements |
| G105 | 105,000 | 135,000 | 115,000 | — | Deep wells, high-torque directional drilling |
| S135 | 135,000 | 165,000 | 145,000 | — | Ultra-deep, extended-reach, and HPHT wells |
Critical Engineering Point — Sour Service (H₂S) RestrictionsHigh-strength grades (G105 and S135) are susceptible to sulfide stress cracking (SSC) in environments containing hydrogen sulfide (H₂S). Where well conditions require sour service compliance per NACE MR0175 / ISO 15156, Grade E75 is typically the maximum permissible grade. Specifying G105 or S135 in H₂S-containing wells without SSC-qualified material is a known failure mode. Always confirm sour service applicability with your drilling engineer before specifying grade.
Grade Identification Markings
API 5DP requires drill pipe to be stencil-marked on the tube body with: the manufacturer's name or mark, the API monogram (where licensed), the grade designation, the heat/lot number, and the size (OD × wall thickness). Tool joints are separately marked with OD, bore, and connection type. These markings are the primary means of field identification — verify them on receipt before running pipe in hole.
3. Standard OD Sizes and Wall Thicknesses
API 5DP covers drill pipe in nominal OD sizes from 2-3/8 inch through 6-5/8 inch. For each OD, one or more nominal wall thicknesses are specified, producing different weight classes. The table below covers the most widely used size and weight combinations in commercial drilling operations.
| Nominal OD (in) | OD Tolerance | Nominal Wall Thickness (in) | Weight Class | ID (approx., in) | Cross-Section Area (in²) |
| 2-3/8 | +0.031 / −0.031 | 0.280 | Standard | 1.815 | 1.812 |
| 2-7/8 | +0.031 / −0.031 | 0.362 | Standard | 2.151 | 2.858 |
| 3-1/2 | +0.031 / −0.031 | 0.368 | Standard | 2.764 | 3.621 |
| 4 | +0.031 / −0.031 | 0.330 | Standard | 3.340 | 3.805 |
| 4-1/2 | +0.031 / −0.031 | 0.337 | Standard | 3.826 | 4.407 |
| 5 | +0.031 / −0.031 | 0.362 | Standard | 4.276 | 5.275 |
| 5-1/2 | +0.031 / −0.031 | 0.415 | Standard | 4.670 | 6.630 |
| 5-7/8 | +0.031 / −0.031 | 0.500 | Standard | 4.875 | 8.449 |
| 6-5/8 | +0.047 / −0.047 | 0.500 | Standard | 5.625 | 9.598 |
Engineering Insight — OD Selection and HydraulicsDrill pipe OD selection is constrained by both the casing program (the pipe must pass through the previous casing string) and hydraulics (annular velocity must be sufficient to lift cuttings). For a given casing ID, larger drill pipe OD improves torsional and tensile capacity but reduces annular clearance. Most deepwater programs use 5 inch or 5-1/2 inch drill pipe in the main string as a balance between hydraulic performance and mechanical strength.
4. Drill Pipe Weight Per Foot
Drill pipe weight is expressed as nominal weight in pounds per foot (lb/ft) and is a critical input for hook load calculations, buoyancy calculations, and buckling analysis. The nominal weight includes the tube body weight plus an allowance for the upset ends and tool joints, averaged over the joint length.
| Nominal OD (in) | Nominal Wall (in) | Nominal Weight (lb/ft) | Plain-End Weight (lb/ft) | Approx. Joint Length (ft) | Approx. Joint Weight (lb) |
| 2-3/8 | 0.280 | 6.65 | 6.26 | 30 | ~200 |
| 2-7/8 | 0.362 | 10.40 | 9.72 | 30 | ~312 |
| 3-1/2 | 0.368 | 13.30 | 12.31 | 30 | ~399 |
| 4 | 0.330 | 14.00 | 12.93 | 30 | ~420 |
| 4-1/2 | 0.337 | 16.60 | 15.00 | 30 | ~498 |
| 5 | 0.362 | 19.50 | 17.93 | 30 | ~585 |
| 5-1/2 | 0.415 | 24.70 | 22.54 | 30 | ~741 |
| 6-5/8 | 0.500 | 33.93 | 31.03 | 30 | ~1,018 |
Procurement Note — Weight AccountingWhen calculating total drill string weight for rig capability assessment, use nominal weight (not plain-end weight) for the tube body, and add the actual tool joint weight separately. Tool joint weight can represent 10–20% of total joint weight on smaller-diameter pipe. Vendors quoting "adjusted weight" may include the tool joint contribution differently — always confirm the basis before loading into your hook load model.
5. Tool Joint Specifications
Tool joints are the threaded connection elements at each end of a drill pipe joint. The pin (male thread) is at the lower end; the box (female thread) is at the upper end. Tool joints are manufactured separately from high-alloy steel (typically AISI 4145H modified) and friction-welded to the upset tube ends. They must be harder and stronger than the pipe body to resist the repeated make-up and break-out cycles experienced over the pipe's service life.
Tool Joint OD and ID
Tool joint OD must be large enough to provide adequate torsional strength but small enough to pass through the casing string and not create excessive equivalent circulating density (ECD) restrictions in the annulus. Tool joint ID must be sufficient for target flow rates without excessive pressure drop.
| Pipe OD (in) | Typical TJ OD (in) | Typical TJ ID (in) | Common Connection Type | TJ OD/Pipe OD Ratio |
| 2-3/8 | 3-1/2 | 1-3/8 | NC26 | 1.47 |
| 2-7/8 | 3-3/4 | 1-3/4 | NC31 | 1.30 |
| 3-1/2 | 4-3/4 | 2-1/4 | NC38 | 1.36 |
| 4 | 5-1/4 | 2-9/16 | NC40 / NC46 | 1.31 |
| 4-1/2 | 6-1/4 | 3 | NC46 / NC50 | 1.39 |
| 5 | 6-5/8 | 3-1/4 | NC50 | 1.33 |
| 5-1/2 | 7-1/4 | 3-1/2 | 5-1/2 FH | 1.32 |
| 6-5/8 | 8-1/4 | 4 | 6-5/8 FH | 1.24 |
Tool Joint Thread Profiles
The dominant thread profile for drill pipe tool joints is the API Rotary Shouldered Connection (RSC), specifically the Numbered Connection (NC) series. NC connections are identified by a two-digit number approximately equal to the pitch diameter of the pin thread in tenths of an inch. Full-Hole (FH) connections are used on larger OD pipe where maximum bore ID is required. Premium non-API connections (e.g., Grant Prideco XT, TenarisHydril Blue) offer enhanced torque capacity for high-performance applications but require licensing from connection manufacturers.
6. Range Lengths
API defines three range length categories for drill pipe. Range selection affects tripping speed (longer joints = fewer connections to make/break), stand-back height requirements in the derrick, and pipe handling equipment specifications.
Range 1 (R1)
Length: 18 – 22 ft (5.5 – 6.7 m)
Typical use: Shallow wells, coiled tubing operations, workover
Note: Rarely used in modern rotary drilling
Range 2 (R2)
Length: 27 – 30 ft (8.2 – 9.1 m)
Typical use: Standard onshore and offshore rotary drilling
Note: Industry default; 95%+ of drill pipe shipments
Range 3 (R3)
Length: 38 – 45 ft (11.6 – 13.7 m)
Typical use: Deepwater, extended-reach, and ultra-deep wells
Note: Requires tall derrick and double/triple stand racking
Engineering Insight — Range 3 Trip Time SavingsOn a 20,000 ft well using 30 ft Range 2 joints, there are approximately 667 connections to trip out of hole. The same well with Range 3 joints (42 ft average) requires only ~476 connections — a reduction of nearly 30%. At 3–5 minutes per connection, this represents 3–6 hours saved per trip. For deepwater operations where rig day rates exceed $500,000, Range 3 adoption has clear economic justification despite the higher derrick height requirement.
7. Heavy Weight Drill Pipe (HWDP)
Heavy Weight Drill Pipe (HWDP) occupies the transition zone between the drill collars at the bottom of the BHA and the standard drill pipe string above. It is visually similar to standard drill pipe but has a significantly thicker wall, a central upset (wear pad) in the middle of the tube body, and larger-diameter tool joints. Its primary function is to reduce the fatigue failures that occur at the transition from the rigid drill collar section to the more flexible standard drill pipe.
| Nominal OD (in) | Wall Thickness (in) | Nominal Weight (lb/ft) | ID (in) | Joint Length (ft) | Approx. Joint Weight (lb) |
| 3-1/2 | 0.615 | 25.3 | 2.25 | 30 | ~759 |
| 4 | 0.670 | 30.0 | 2.56 | 30 | ~900 |
| 4-1/2 | 0.750 | 41.0 | 3.00 | 30 | ~1,230 |
| 5 | 0.750 | 49.3 | 3.50 | 30 | ~1,479 |
| 5-1/2 | 0.750 | 55.0 | 4.00 | 30 | ~1,650 |
Field Note — HWDP String LengthIndustry rule of thumb calls for a minimum HWDP section of 30–40 joints (approximately 900–1,200 ft) above the drill collars. In directional wells with high dogleg severity, longer HWDP sections are used to protect the transition zone from cyclic bending fatigue. Under-specifying HWDP length is a common cause of drill string fatigue failures at the top of the BHA.
8. Grade Selection Guide
Grade selection involves balancing tensile capacity, torsional strength, fatigue resistance, and sour-service compatibility against cost. The following matrix summarizes the primary selection drivers for each API 5DP grade.
| Selection Factor | E75 | X95 | G105 | S135 |
| Shallow wells (<8,000 ft) | Preferred | Acceptable | Overspec | Overspec |
| Medium wells (8,000–15,000 ft) | Marginal | Preferred | Acceptable | Overspec |
| Deep wells (>15,000 ft) | Insufficient | Marginal | Preferred | Preferred |
| Extended-reach / ERD wells | Insufficient | Marginal | Acceptable | Preferred |
| Sour service (H₂S present) | Qualified | Verify NACE | Not recommended | Not recommended |
| HPHT wells | Insufficient | Insufficient | Marginal | Preferred |
| Cost sensitivity | Lowest cost | Low-moderate | Moderate | Highest cost |
Critical Engineering Point — Don't Underspec for Cost SavingsSelecting a lower grade to reduce upfront cost is one of the more consequential procurement errors in drill pipe purchasing. A Grade E75 string that fails at depth in a 15,000 ft well costs orders of magnitude more in fishing operations, potential sidetrack, and rig time than the cost differential between E75 and X95 on the original order. Mechanical sizing calculations by a qualified drilling engineer should always precede grade selection on any well beyond routine shallow depths.
9. Frequently Asked Questions
What are the standard grades of drilling pipe per API 5DP?
API 5DP specifies four standard drill pipe grades: E75 (minimum yield 75,000 psi), X95 (minimum yield 95,000 psi), G105 (minimum yield 105,000 psi), and S135 (minimum yield 135,000 psi). Grade selection depends on well depth, directional complexity, and required torsional and tensile capacity. S135 is the highest commercially available standard grade and is used for demanding extended-reach and HPHT applications.
What OD sizes are available for API drill pipe?
Standard API 5DP drill pipe OD sizes range from 2-3/8 inch through 6-5/8 inch. The most commonly used sizes in oil and gas drilling are 3-1/2 inch, 4 inch, 4-1/2 inch, and 5 inch. Larger sizes such as 5-1/2 inch and 5-7/8 inch are specified for high-flow or high-torque applications where larger bore is required.
What is the difference between drill pipe range lengths?
API defines three range lengths: Range 1 (18–22 ft), Range 2 (27–30 ft), and Range 3 (38–45 ft). Range 2 is the industry standard for the vast majority of rotary drilling operations. Range 3 is specified for deepwater and ultra-deep wells where fewer connections per trip meaningfully reduce non-productive rig time.
What wall thickness classifications exist for drill pipe?
Standard drill pipe uses nominal wall thicknesses ranging from 0.280 inch (2-3/8 OD) to 0.500 inch (5-7/8 and 6-5/8 OD) depending on size. Heavy Weight Drill Pipe (HWDP) uses significantly thicker walls — typically 0.615 to 0.750 inch for the same OD range — along with a central wear pad and larger tool joints. HWDP is specified for the transition zone above drill collars to reduce fatigue failures.
Is drilling pipe the same as drill pipe?
Yes — "drilling pipe" and "drill pipe" are used interchangeably throughout the industry. Both terms refer to the hollow steel pipe joints that form the main body of the drill string in a rotary drilling operation. The official API standard is titled "Specification for Drill Pipe" (API 5DP). The term "drilling pipe" is more common in non-English speaking markets and in translated procurement documents.
Request Drill Pipe Specifications & Pricing
ZC Steel Pipe manufactures API 5DP drill pipe in all standard grades (E75, X95, G105, S135) and OD sizes, with Range 2 and Range 3 available. As an order-to-make manufacturer based in Hai'an City, China, we serve drilling contractors and OCTG buyers across Africa, the Middle East, and South America.
Contact us with your well program requirements — grade, OD, wall thickness, range length, quantity, and delivery destination — and our technical team will respond with specifications and a competitive quote.
mandy.w@zcsteelpipe.com | WhatsApp: +86-139-1579-1813
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