Flange Weight Calculator (ASME B16.5)
Calculate the theoretical weight of ASME B16.5 pipe flanges from true 3-D geometry — tapered weld-neck hubs and raised faces included, not a flat-plate approximation. Covers Weld Neck, Slip On, Blind, Socket Weld and Threaded flanges, Class 150–2500, NPS 1/2″–24″.
Tapered hub, butt-weld end
Single Flange Weight
–kg
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Key Dimensions (ASME B16.5)
Volume Breakdown
Data source
Dimensions per ASME B16.5-2020: WN Table 8, SO Table 9, SW Table 10, BL Table 12, THD Table 15 (Class 150/300), equivalent class tables for 600–2500. Bore = STD-wall pipe ID per ASME B36.10M.
ASME B16.5 Flange Dimensions & Weights — Class 150
| NPS | OD (mm) | Bore (mm) | t / C (mm) | X (mm) | Y (mm) | Bolt Circle (mm) | Bolts | Weight (kg) |
|---|
Weights in the table use the currently selected material density. Tap any row to load it into the calculator.
How the calculation works (geometric model, not flat plate)
Volume equations (dimensions from ASME B16.5 tables)
- Weld Neck: V = disc(OD, bore, t) + frustum(X→OD, Y−t) − bore cylinder(Y−t) + raised face
- Slip On / Socket Weld / Threaded: V = disc(OD, bore, t) + cylinder(X, Y−t) − bore cylinder(Y−t) + raised face
- Blind: V = disc(OD, tblind) + raised face
- Frustum: V = π·L/3 · (R₁² + R₁R₂ + R₂²)
- Weight = V × ρ × 10⁻⁹ (mm³ → kg, ρ in kg/m³)
The flat-plate method (π/4·(OD²−bore²)·t·ρ) ignores the hub. For a 24″ Class 150 WN flange it returns ≈ 90 kg versus the true ≈ 128 kg — a 42% understatement, which is why geometric modeling matters for freight and quoting.
Frequently Asked Questions
How do you calculate the weight of an ASME B16.5 flange?+
The weight is calculated from the true 3-D volume of the flange multiplied by material density. The flange is decomposed into a flange ring disc, a tapered (weld neck) or straight (slip-on) hub, and the raised face, using the official ASME B16.5 dimensions — outside diameter, bore, ring thickness t, hub diameter X, hub length Y. Weight = Volume × Density. This is fundamentally more accurate than the flat-plate method used by most online calculators.
Why is this calculator more accurate than flat-plate (plate approximation) calculators?+
Flat-plate calculators compute weight as π/4 × (OD² − bore²) × thickness × density, ignoring the hub entirely. For a 24" Class 150 weld neck flange that method understates the weight by more than 40%. Our engine models the conical frustum hub and raised face explicitly, which typically lands within ±5% of manufacturer catalog weights.
What is the difference between weld neck and slip-on flange weight?+
For the same NPS and class, weld neck flanges are usually heavier because their hub is a full-length tapered cone (long dimension Y) designed for butt welding and fatigue resistance, while slip-on flanges have a shorter straight hub. The ring (flange body) dimensions O, t and bolt circle are identical between WN and SO in ASME B16.5 for Class 150 and 300.
How much does a 24 inch 150# weld neck flange weigh?+
A 24" (NPS 24) Class 150 weld neck flange in ASTM A105 carbon steel weighs approximately 128 kg (about 282 lb) by ASME B16.5 geometric calculation — consistent with major manufacturer catalogs (typically quoted around 126–129 kg).
How much does a 24 inch class 150 blind flange weigh?+
A 24" Class 150 blind flange (ASME B16.5 blind minimum thickness 69.9 mm / 2.75 in) in A105 carbon steel weighs approximately 291 kg (about 642 lb). Be careful with calculators showing values near 193 kg — they mistakenly apply the weld-neck ring thickness instead of the blind thickness.
What material densities are used in this calculator?+
ASTM A105 carbon steel: 7,850 kg/m³; ASTM A182 F304 stainless steel: 8,000 kg/m³; ASTM A182 F316/F316L: 7,980 kg/m³; ASTM A182 F11 alloy steel: 7,820 kg/m³; ASTM A182 F22: 7,850 kg/m³. A custom density input (kg/m³ or lb/ft³ equivalent) is also available.
Which flange types, classes and sizes are covered?+
All five ASME B16.5 flange types — Weld Neck (WN), Slip On (SO), Blind (BL), Socket Weld (SW) and Threaded (THD) — in Class 150, 300, 600, 900, 1500 and 2500. NPS 1/2" through 24" are covered, with the same size exclusions as the standard itself (no 3-1/2" in Class 900/1500, and Class 2500 stops at NPS 12").
Does the calculator include the raised face and hub taper?+
Yes. The raised face (1.6 mm for Class 150/300, 6.4 mm for Class 600 and above) is added as an explicit annular volume, and weld neck hubs are modeled as true conical frustums between the hub base diameter X and the flange outside diameter over the hub length Y minus ring thickness.
How accurate is this calculator?+
For standard ASME B16.5 flanges in carbon steel, calculated weights are typically within ±5% of published manufacturer catalog weights (e.g., 24" 150# WN ≈ 128 kg vs 126–129 kg catalog). Deviations come from bore selection (we use STD-wall pipe bore), fillet radii, and manufacturing tolerances. For critical applications, always verify with the manufacturer.
Are bolt holes subtracted from the flange weight?+
No. ASME B16.5 bolt-circle hole deduction is negligible (typically under 0.5% of total weight) and standard manufacturer catalog weights are quoted without deducting bolt holes, so we follow the same convention for consistency with supplier quotations.
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Disclaimer: Calculated weights are theoretical values based on ASME B16.5-2020 dimensions and nominal material densities. Actual weights may vary due to bore selection, fillet radii, and manufacturing tolerances. For critical applications (lifting, shipping cost guarantees, pressure-boundary design), verify with the flange manufacturer.