Threaded Steel Pipe Nipples: Sizes, Dimensions & Compatibility Chart
Threaded steel pipe nipples are essential components in plumbing, oil & gas, HVAC, and industrial piping systems. They provide secure, leak-proof connections between pipes, valves, and fittings. Choosing the right size, material, and thread type is critical for system integrity.
This guide covers:
Standard sizes & dimensions (NPT, BSP, metric)
Material compatibility (carbon steel, stainless, galvanized)
Pressure ratings & temperature limits
Thread standards (NPT vs. BSP vs. metric)
Downloadable sizing chart
Standard Threaded Steel Pipe Nipple Sizes
Threaded pipe nipples come in various lengths and diameters, categorized by:
A. Nominal Pipe Size (NPS)
| NPS (inches) |
Actuall OD (inches) |
Threads per INCH(TPI) |
| 1/8 | 0.405 | 27 |
| 1/4 | 0.54 | 18 |
| 3/8 | 0.675 | 18 |
| 1/2 | 0.84 | 14 |
| 3/4 | 1.05 | 14 |
| 1 | 1.315 | 11.5 |
| 1 1/2 | 1.9 | 11.5 |
| 2 | 2.375 | 11.5 |
B. Common Lengths
Close nipple (shortest, fully threaded)
Short nipple (1–2″ longer than close)
Long nipple (custom lengths up to 12″)
Thread Standards & Compatibility
A. NPT (National Pipe Thread) – USA Standard
Tapered threads (seal via thread deformation)
Common in North America
Requires thread sealant (Teflon tape, pipe dope)
B. BSP (British Standard Pipe) – Global Use
BSPT (tapered) & BSPP (parallel)
Common in Europe, Asia, Australia
Not interchangeable with NPT
C. Metric Threads (ISO 228/7)
Used in machinery & automotive
M-style threads (e.g., M10, M12)
⚠ Warning: Mixing NPT and BSP can cause leaks! Always verify thread type.
Material Selection Guide
Carbon steel
Stainless steel 304 & 304L
Stainless steel 316 & 316L
The stainless steel pipe nipple size chart
Material: ASTM A312, Type 304/304L or 316/316L ；Welded or Seamless
Threads: ANSI/ASME B 1.20.1
| Pipe Size |
B | A. Length | ||||||||||||||||
| Pipe O.D. |
Close | Space | ||||||||||||||||
| 1/8 | 0.405 | 3/4 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 1/4 | 0.54 | 7/8 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 3/8 | 0.675 | 1 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 1/2 | 0.84 | 1 1/8 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 3/4 | 1.05 | 1 3/8 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 1 | 1.315 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
| 1 1/4 | 1.66 | 1 5/8 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
| 1 1/2 | 1.9 | 1 3/4 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
| 2 | 2.375 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ||
| 2 1/2 | 2.875 | 2 1/2 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |||
| 3 | 3.5 | 2 5/8 | 3 | 3 1/2 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |||
| 4 | 4.5 | 2 7/8 | 4 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |||||
| 5 | 5.563 | 3 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ||||||
| 6 | 6.625 | 3 1/8 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ||||||
| 8 | 8.625 | 3 1/2 | 4 1/4 | 5 | 5 1/2 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ||||||
Pressure & Temperature Ratings
Schedule 40: Standard for general plumbing (300–1000 PSI)
Schedule 80: High-pressure industrial use (1000–3000 PSI)
Temperature Limits:
Carbon steel: Up to 500°F (260°C)
Stainless steel: Up to 800°F (427°C)
How to Measure a Threaded Nipple
1. Determine Nominal Pipe Size (NPS) – Measure outer diameter (OD).
2. Check Thread Pitch– Use a thread gauge (TPI for NPT, pitch for metric).
3. Verify Length – Measure from end to end (including threads).
📌 Pro Tip: Always use a thread sealant (Teflon tape for NPT, Loctite for BSPP).
Common Applications
✔ Plumbing – Connecting water lines, valves
✔ Oil & Gas – High-pressure pipe joints
✔ HVAC – Refrigerant & steam lines
✔ Industrial Machinery** – Hydraulic fittings
Where to Buy Quality Threaded Nipples
– ASTM A53 (Carbon steel)
– ASTM A312 (Stainless steel)
– API 5L (Oil & gas certified)
Final Thoughts
Thread type (NPT/BSP/Metric)
Material (carbon/stainless/galvanized)
Pressure & temperature requirements
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