Calculate the weight of circular and rectangular flanges using inside dimensions, flange width, thickness, material density and quantity. This calculator is useful for HVAC ducting, industrial piping, fabrication, material estimation, procurement and bill of material (BOM) preparation.
Last Updated: July 14, 2026
A flange is a circular ring or rectangular frame used to connect ducts, pipes, equipment and fabricated structures. Flanges provide a rigid bolted or welded connection while maintaining dimensional accuracy during installation. The weight of a flange depends on its centre line length, cross-sectional area, material density and quantity.
This calculator determines the flange centre line length from the entered dimensions. It then calculates the cross-sectional area using the flange width and thickness. The flange volume is obtained by multiplying the cross-sectional area by the centre line length, and the weight is calculated by multiplying the volume by the selected material density.
Cross-sectional Area = Flange Width × Flange Thickness
Volume = Cross-sectional Area × Centre Line Length
Weight = Volume × Material Density
| Parameter | Formula |
|---|---|
| Outside Length | Inside Length + 2 × Flange Width |
| Outside Width | Inside Width + 2 × Flange Width |
| Centre Line Length | 2 × [(Inside Length + Flange Width) + (Inside Width + Flange Width)] |
| Parameter | Formula |
|---|---|
| Centre Line Diameter | Inside Diameter + Flange Width |
| Centre Line Length | π × (Inside Diameter + Flange Width) |
| Material | Typical Density (kg/m³) |
|---|---|
| Mild Steel (General) | 7850 |
| IS 2062 Structural Steel | 7850 |
| Carbon Steel | 7850 |
| Stainless Steel 304 | 8000 |
| Stainless Steel 316 | 8000 |
| Stainless Steel 316L | 8000 |
| Stainless Steel 409 | 7750 |
| Aluminium | 2700 |
| Cast Iron | 7200 |
| Copper | 8940 |
| Brass | 8500 |
| Bronze | 8800 |
| Titanium | 4500 |
| Nickel | 8900 |
| Standard | Application |
|---|---|
| SMACNA | HVAC duct construction |
| DW/144 | Sheet metal ductwork |
| IS 2062 | Structural steel |
| ASTM A36 | Carbon steel |
| ASME B16.5 | Pipe flanges |
The calculator determines the flange centre line length, calculates the cross-sectional area from the flange width and thickness, determines the flange volume, and multiplies it by the selected material density to calculate the flange weight.
Yes. The calculator supports both circular and rectangular flanges. Simply select the required flange type and enter the corresponding dimensions.
Yes. All dimensions, including inside length, inside width, inside diameter, flange width and flange thickness, must be entered in millimetres (mm).
No. The calculated weight is based only on the flange geometry. Bolt holes, welds, bolts, nuts, gaskets and other fabrication details are not included.
Yes. It is suitable for HVAC duct flanges, industrial ventilation systems, industrial piping, bag filter ductwork and general fabrication applications.
The result is the theoretical flange weight based on the entered dimensions and material density. Manufacturing tolerances, machining and fabrication allowances are not included.
Yes. The calculated flange weight can be used for bill of materials (BOM) preparation, material estimation, procurement planning, transportation studies and preliminary fabrication cost estimation.