How the calculator works out the weight
Weight = cross-section area x length x density
The calculator works out the area of the shape and multiplies it by the length to get the volume. Then it multiplies by the density of the metal. Each shape has its own area formula.
| Shape | Cross-section area |
|---|---|
| Plate or sheet | thickness x width |
| Round bar | pi / 4 x diameter² |
| Square bar | side² |
| Flat bar | width x thickness |
| Hex bar | 0.866 x (size across flats)² |
| Round tube | pi / 4 x (OD² - ID²), with ID = OD - 2 x wall |
| Square or rectangular tube | W x H - (W - 2t) x (H - 2t) |
| Angle | (leg A + leg B - t) x t |
The tube and angle formulas use sharp corners. Rolled and extruded shapes have corner radii, so a catalogue weight can differ by a percent or two. Russel Metals lists 4 x 4 x 0.125 in square HSS at 6.46 lb per foot, where the sharp-corner formula gives 6.59.
Densities used
| Metal | Density | In lb/in³ | Source |
|---|---|---|---|
| Carbon steel | 7,850 kg/m³ | 0.2836 | Russel Metals |
| Stainless 304 | 7,900 kg/m³ | 0.2854 | Outokumpu |
| Stainless 316 | 8,000 kg/m³ | 0.2890 | Outokumpu |
| Aluminum 6061 | 2,700 kg/m³ | 0.0975 | Kaiser Aluminum |
| Aluminum 5052 | 2,680 kg/m³ | 0.0968 | Smiths Metal Centres |
| Aluminum 3003 | 2,730 kg/m³ | 0.0986 | Kaiser Aluminum |
| Aluminum 7075 | 2,800 kg/m³ | 0.1012 | Kaiser Aluminum |
| Brass C360 | 8,500 kg/m³ | 0.307 | Copper Development Association |
| Brass C260 | 8,530 kg/m³ | 0.308 | Copper Development Association |
| Copper C110 | 8,910 kg/m³ | 0.322 | Copper Development Association |
For 304 stainless, Cleveland-Cliffs lists 8.03 g/cm³, about 1.6 percent above Outokumpu's 7.9. Kaiser Aluminum rounds its imperial values to 0.098, 0.099 and 0.101 lb per cubic inch, and the calculator uses the metric ones. The copper alloys use the specific gravity on each Copper Development Association page.
Worked examples
Round bar, inches. Take ten 1 in carbon steel round bars, 12 ft long. The area is 0.7854 square inches, so a foot weighs 0.7854 x 12 x 0.2836 = 2.673 lb. Each bar weighs 32.07 lb, and the ten weigh 320.7 lb. Russel Metals lists 1 in cold finished round at 2.67 lb per foot.
Round bar, millimetres. Take ten 25 mm round bars, 6 m long. The area is 490.9 square millimetres, so a metre weighs 3.853 kg. Each bar weighs 23.12 kg, and the ten weigh 231.2 kg.
Tube. A 0.75 in tube with a 0.065 in wall weighs 0.476 lb per foot by the formula. Russel Metals' mechanical tubing table lists the same 0.476 lb.
Hex and angle. The formulas give 2.947 lb per foot for a 1 in hex bar and 3.190 lb for a 2 x 2 x 1/4 in angle. Russel Metals lists 2.95 lb and 3.19 lb.
How the metals compare
For the same size, 6061 aluminum weighs 34 percent as much as carbon steel. C360 brass weighs 8 percent more than steel, and C110 copper 14 percent more. Stainless 304 weighs less than 1 percent more than carbon steel at the densities used here.
Material cost
Enter a price per kilogram or per pound, and the calculator adds the material cost of each piece and of the whole quantity. It multiplies the theoretical weight by your price, so cutting, drops and freight stay out of it.
The guide to costing software for manufacturing covers how a plant builds a part's full cost on top of its material.
Questions
How do you calculate the weight of metal?
How much does a foot of 1 in steel round bar weigh?
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Which density does the calculator use for stainless?
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