Rectangular flange
Lₒ = 2[(L + Wf) + (W + Wf)]
The existing calculator uses the rectangular centre-line length based on inside dimensions and face width Wf.
Existing engineering calculator
Flange Weight Calculator
Estimate the weight of a rectangular or circular flange from its internal geometry, face width, thickness, selected material density and quantity.
Calculator inputs and result
Select flange geometry, enter the internal dimensions and cross-section, then choose material and quantity. The existing result reports the single and total weight.
For a fabricated plate flange, select the actual plate material. Cast flanges require a separate geometry and material model.
Engineering knowledge
Flange centre-line length, section and material weight
A flange is a rectangular frame or circular ring used to join ductwork, piping or fabricated equipment. Its mass is determined by the material cross-section, centre-line length, density and quantity. The calculation is useful for early material estimates, but final flange assemblies may include bolts, holes, weld metal, gaskets, coatings and other components that must be assessed separately.
Related calculation knowledge
Use actual geometry and verified material data for work that affects procurement, lifting, support loads or fabrication release.
Read the Duct Weight Calculator guidance →Input and result definitions
Internal geometryRectangular flanges use inside length and width; circular flanges use inside diameter.
Cross-sectionFace width and thickness define the material cross-section used by the existing calculator.
ResultThe result reports centre-line length, one flange weight, quantity and total mass.
Formula and calculation method
Circular flange
Lₒ = π(D + Wf)
D is internal diameter and Wf is face width, using the existing centre-line approximation.
Mass relation
m = Lₒ × Wf × t × ρ
All dimensions are converted consistently by the implemented calculator before density is applied.
Assumptions and limitations
- The result estimates the main flange material only; bolting, holes, welds, gaskets, stiffeners and surface treatments are excluded.
- The calculator uses a simplified centre-line relation, suitable for preliminary estimates rather than fabrication release.
- Material densities are existing indicative values and do not replace certified project data.
- Final connection design, pressure service, support design and fabrication documentation need applicable standards and qualified review.
Illustrative use case
For a rectangular flange with 1,000 mm inside length, 800 mm inside width, 50 mm face width, 10 mm thickness and mild steel density, the existing relation gives a 3.800 m centre-line length and an approximate single-flange mass of 14.91 kg. Bolts, holes and connection details are not included.
Frequently asked questions
Does the result include bolts and gaskets?
No. The output is for the main flange material only. Add all connection hardware separately for a complete assembly weight.
Can this calculator be used for pipe flanges?
It provides a simplified ring or frame material estimate. Standard pipe flange dimensions and pressure ratings must be selected from the relevant standard and manufacturer data.
Why is quantity needed?
Quantity scales the calculated weight of one flange to an estimated total mass for the stated number of identical parts.
References
- Oberg, E., Jones, F. D., Horton, H. L. and Ryffel, H. H. Machinery's Handbook. 30th ed. Industrial Press. 2016.
- American Institute of Steel Construction. Steel Construction Manual. 15th ed. AISC. 2017.
This is an original educational summary. Verify material certification and project requirements for actual work.
Review information
Content type: existing engineering calculator with knowledge module.Interface reviewed: 27 August 2026. Technical review is required before project use, procurement, construction, operation, compliance or safety decisions.
Engineering disclaimer
Educational and preliminary engineering-reference use only.This calculator does not replace project specifications, detailed design, fabrication drawings, applicable standards or review by a qualified engineer. Verify all values, assumptions and decisions for actual service conditions.