ASME B16.5 Flange Weight Chart (kg & lb)
Theoretical weights for all ASME B16.5 flange types — Weld Neck, Slip On, Blind, and Socket Weld — in every Class (150–2500) and size (NPS ½"–24"), computed from true 3D geometry. Material: carbon steel A105, 7,850 kg/m³.
← Scroll tables horizontally to see all NPS sizes →
Weld Neck (WN)
Tapered conical hub, butt-weld end. Preferred for high-pressure, high-temperature, and cyclic service. Hub geometry makes it the heaviest non-blind type.
| Class | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" | 5" | 6" | 8" | 10" | 12" | 14" | 16" | 18" | 20" | 22" | 24" |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 150 | 0.6 | 0.8 | 1.1 | 1.4 | 1.7 | 2.6 | 4.3 | 5.0 | 6.3 | 7.1 | 8.7 | 10.3 | 16.8 | 23.8 | 38.4 | 49.7 | 65.3 | 72.0 | 93.0 | 108.6 | 127.7 |
| 300 | 1.0 | 1.6 | 2.1 | 2.7 | 3.7 | 4.5 | 6.6 | 8.6 | 11.0 | 13.0 | 16.5 | 21.4 | 30.7 | 45.9 | 66.3 | 92.8 | 119.0 | 145.8 | 179.8 | 218.6 | 272.9 |
| 600 | 1.0 | 1.5 | 2.1 | 2.6 | 3.6 | 4.6 | 6.8 | 9.1 | 11.8 | 18.4 | 30.1 | 36.7 | 55.7 | 91.8 | 112.1 | 135.7 | 188.5 | 232.2 | 295.7 | 347.7 | 427.2 |
| 900 | 2.3 | 3.0 | 4.4 | 5.1 | 7.0 | 12.8 | 18.4 | 14.7 | — | 26.4 | 42.9 | 53.8 | 93.3 | 137.7 | 187.3 | 220.8 | 274.7 | 364.0 | 456.2 | 561.6 | 796.2 |
| 1500 | 2.3 | 3.0 | 4.5 | 5.1 | 7.0 | 12.8 | 18.4 | 24.0 | — | 36.8 | 65.8 | 80.1 | 137.8 | 238.9 | 360.2 | 482.2 | 629.9 | 830.0 | 1016.2 | 1243.2 | 1599.4 |
| 2500 | 3.7 | 4.2 | 5.9 | 8.9 | 12.7 | 19.2 | 27.1 | 41.5 | — | 64.8 | 107.0 | 164.5 | 242.0 | 453.6 | 632.9 | — | — | — | — | — | — |
All weights in kg. Carbon steel A105, 7,850 kg/m³. — = size not covered by this class in ASME B16.5.
Slip On (SO)
Slides over pipe, secured by two fillet welds. Ring OD and bolt circle identical to WN for Class 150/300. Lighter than WN due to shorter, straight hub.
| Class | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" | 5" | 6" | 8" | 10" | 12" | 14" | 16" | 18" | 20" | 22" | 24" |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 150 | 0.5 | 0.7 | 1.0 | 1.2 | 1.5 | 2.3 | 3.9 | 4.5 | 5.7 | 6.3 | 7.5 | 9.1 | 14.7 | 20.6 | 32.2 | 42.1 | 54.1 | 60.6 | 77.9 | 91.8 | 107.7 |
| 300 | 0.8 | 1.4 | 1.8 | 2.3 | 3.3 | 4.1 | 6.0 | 7.9 | 10.2 | 11.6 | 14.8 | 19.5 | 28.4 | 42.5 | 60.6 | 84.3 | 107.5 | 130.6 | 159.8 | 193.1 | 240.3 |
| 600 | 0.8 | 1.2 | 1.6 | 2.2 | 3.0 | 3.9 | 5.8 | 7.8 | 10.1 | 15.8 | 26.2 | 32.0 | 49.1 | 81.6 | 99.4 | 119.4 | 165.6 | 204.0 | 260.3 | 306.8 | 375.6 |
| 900 | 1.8 | 2.5 | 3.7 | 4.2 | 5.9 | 10.7 | 15.2 | 12.5 | — | 21.7 | 35.4 | 44.8 | 76.2 | 112.6 | 154.6 | 185.2 | 228.6 | 302.6 | 379.7 | 467.9 | 687.3 |
| 1500 | 1.8 | 2.5 | 3.8 | 4.2 | 5.9 | 10.7 | 15.2 | 19.9 | — | 30.4 | 57.8 | 70.9 | 119.1 | 205.2 | 314.2 | 418.6 | 544.3 | 716.7 | 879.3 | 1091.1 | 1391.6 |
| 2500 | 3.2 | 3.6 | 5.2 | 7.6 | 10.9 | 16.9 | 24.1 | 37.4 | — | 57.9 | 96.4 | 148.9 | 220.8 | 422.0 | 587.1 | — | — | — | — | — | — |
All weights in kg. Carbon steel A105, 7,850 kg/m³. — = size not covered by this class in ASME B16.5.
Blind (BL)
Solid plate to close pipeline ends or vessel nozzles. Full disc cross-section makes it the heaviest per size — minimum thickness tBl exceeds WN ring thickness t.
| Class | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" | 5" | 6" | 8" | 10" | 12" | 14" | 16" | 18" | 20" | 22" | 24" |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 150 | 0.6 | 0.8 | 1.1 | 1.3 | 1.7 | 2.7 | 4.6 | 5.5 | 7.4 | 9.5 | 12.4 | 16.6 | 28.7 | 44.4 | 70.8 | 91.3 | 123.5 | 153.2 | 195.2 | 237.8 | 291.0 |
| 300 | 0.8 | 1.3 | 1.7 | 2.2 | 3.1 | 3.8 | 5.8 | 7.9 | 10.0 | 13.0 | 17.3 | 24.5 | 40.3 | 63.1 | 94.1 | 129.3 | 167.6 | 210.1 | 262.2 | 322.5 | 398.1 |
| 600 | 0.9 | 1.4 | 1.8 | 2.3 | 3.5 | 4.6 | 6.7 | 9.2 | 12.1 | 18.5 | 31.0 | 41.0 | 64.6 | 105.3 | 140.0 | 170.9 | 237.1 | 303.1 | 388.4 | 473.6 | 585.7 |
| 900 | 2.1 | 2.8 | 4.1 | 4.7 | 6.6 | 11.1 | 15.6 | 14.0 | — | 23.8 | 39.5 | 51.0 | 88.8 | 131.5 | 187.0 | 222.7 | 289.6 | 395.2 | 498.0 | 633.3 | 947.5 |
| 1500 | 2.1 | 2.8 | 4.1 | 4.7 | 6.6 | 11.1 | 15.6 | 21.2 | — | 32.8 | 64.6 | 80.9 | 135.9 | 231.4 | 352.9 | 468.4 | 620.4 | 845.4 | 1074.8 | 1377.5 | 1730.9 |
| 2500 | 3.5 | 3.9 | 5.7 | 8.2 | 11.7 | 17.6 | 25.1 | 38.8 | — | 60.0 | 101.3 | 158.1 | 239.2 | 467.3 | 660.8 | — | — | — | — | — | — |
All weights in kg. Carbon steel A105, 7,850 kg/m³. — = size not covered by this class in ASME B16.5.
Socket Weld (SW)
Counter-bore socket receives pipe end; single fillet weld. Similar geometry and weight to slip-on. Common in NPS ≤ 2" high-pressure small-bore service.
| Class | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 3-1/2" | 4" | 5" | 6" | 8" | 10" | 12" | 14" | 16" | 18" | 20" | 22" | 24" |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 150 | 0.5 | 0.7 | 1.0 | 1.2 | 1.5 | 2.3 | 3.9 | 4.5 | 5.7 | 6.3 | 7.5 | 9.1 | 14.7 | 20.6 | 32.2 | 42.1 | 54.1 | 60.6 | 77.9 | 91.8 | 107.7 |
| 300 | 0.8 | 1.4 | 1.8 | 2.3 | 3.3 | 4.1 | 6.0 | 7.9 | 10.2 | 11.6 | 14.8 | 19.5 | 28.4 | 42.5 | 60.6 | 84.3 | 107.5 | 130.6 | 159.8 | 193.1 | 240.3 |
| 600 | 0.8 | 1.2 | 1.6 | 2.2 | 3.0 | 3.9 | 5.8 | 7.8 | 10.1 | 15.8 | 26.2 | 32.0 | 49.1 | 81.6 | 99.4 | 119.4 | 165.6 | 204.0 | 260.3 | 306.8 | 375.6 |
| 900 | 1.8 | 2.5 | 3.7 | 4.2 | 5.9 | 10.7 | 15.2 | 12.5 | — | 21.7 | 35.4 | 44.8 | 76.2 | 112.6 | 154.6 | 185.2 | 228.6 | 302.6 | 379.7 | 467.9 | 687.3 |
| 1500 | 1.8 | 2.5 | 3.8 | 4.2 | 5.9 | 10.7 | 15.2 | 19.9 | — | 30.4 | 57.8 | 70.9 | 119.1 | 205.2 | 314.2 | 418.6 | 544.3 | 716.7 | 879.3 | 1091.1 | 1391.6 |
| 2500 | 3.2 | 3.6 | 5.2 | 7.6 | 10.9 | 16.9 | 24.1 | 37.4 | — | 57.9 | 96.4 | 148.9 | 220.8 | 422.0 | 587.1 | — | — | — | — | — | — |
All weights in kg. Carbon steel A105, 7,850 kg/m³. — = size not covered by this class in ASME B16.5.
How weights are calculated
Geometric decomposition (ASME B16.5-2020)
- Weld Neck: annular ring disc + conical frustum hub (X → pipe OD over hub length Y−t) − bore cylinder + raised face
- Slip On / Socket Weld: annular ring disc + hollow straight cylinder hub (OD=X, bore=pipe OD) + raised face
- Blind: solid disc (OD, tBl) + solid raised face disc
Frustum: V = π·L/3·(R₁² + R₁R₂ + R₂²) | Weight = V × 7,850 × 10⁻⁹ kg
Why not flat-plate?
The flat-plate shortcut — π/4×(OD²−bore²)×t×ρ — ignores the hub entirely. For a 24″ Class 150 weld neck flange it returns ≈ 90 kg versus the true ≈ 128 kg, a 42% understatement. 3D geometry is the only reliable basis for freight budgets and material take-offs.
Accuracy: typically ±5% vs manufacturer catalog. Deviations come from bore selection (STD-wall assumed), fillet radii, and manufacturing tolerances.
Need weight for a specific material, size or quantity?
The interactive calculator supports A105, F304, F316, F11, F22 and custom density — with copy/share output.
Open Flange Weight Calculator →Frequently Asked Questions
How much does a 6 inch Class 150 weld neck flange weigh in kg?
An NPS 6 Class 150 weld neck flange in ASTM A105 carbon steel weighs approximately 10.3 kg (23 lb). Weights are computed from ASME B16.5-2020 geometry and are typically within ±5% of manufacturer catalog values.
What is the weight of a 4 inch Class 600 blind flange?
An NPS 4 Class 600 blind flange in carbon steel weighs approximately 18.5 kg (41 lb). Blind flanges are the heaviest type per size because their full-disc thickness tBl is greater than the ring thickness of other flange types.
How do I convert flange weight from kg to lb?
Multiply kilograms by 2.20462 to get pounds. The unit toggle above each table switches the display automatically. Example: 128 kg × 2.20462 = 282 lb. For reverse conversion, divide pounds by 2.20462.
Why are Class 600+ flanges heavier than Class 150 for the same NPS?
Higher pressure classes require a thicker ring, a longer hub, and a larger flange OD per ASME B16.5. All three increase the steel volume. Class 600 flanges are typically 2–3× heavier than Class 150 for the same NPS; Class 2500 can be 5–8× heavier.
How is flange weight calculated in this chart?
The chart uses true 3D geometric decomposition, not the flat-plate shortcut. A weld neck flange is split into: (1) annular ring disc: π/4×(OD²−bore²)×t; (2) conical frustum hub: π×L/3×(R₁²+R₁R₂+R₂²); (3) raised face annulus. Weight = Volume (mm³) × 7,850 kg/m³ × 10⁻⁹. The flat-plate method understates weight by 40%+ on large flanges.
What material is used for the weights in this chart?
Carbon steel at 7,850 kg/m³ (matching ASTM A105 and A350 LF2). For stainless steel F304 (8,000 kg/m³) multiply table values by 1.019. For F316/F316L (7,980 kg/m³) multiply by 1.017. Use the Flange Weight Calculator above for exact per-material results.
Does the chart include NPS 3-1/2?
Yes, for Class 150, 300, and 600. ASME B16.5 does not define NPS 3-1/2 for Class 900 or 1500 (those cells show —). Class 2500 covers NPS ½"–12" only; cells above NPS 12 in Class 2500 are also shown as —.
What is the weight difference between weld neck and slip-on flanges?
Weld neck flanges are typically 15–30% heavier than slip-on for the same NPS and class, because the WN tapered hub is longer and its base diameter X is larger than the SO hub. The ring OD, bolt circle, and raised face are the same for WN and SO in Class 150 and 300.