Metal Weight Calculator
Select a metal, pick a shape, enter the dimensions and get the weight instantly. Supports round bar, flat plate, hollow tube, pipe, wire, hexagonal bar, rectangular bar, ring and sphere. Switch between metric and imperial units at any time. Add a price per kg or per lb to get a material cost estimate alongside the weight.
How the metal weight formula works
Every weight calculation follows the same three-step sequence: find the volume of the cross-section, multiply by length to get total volume, then multiply by the density of the chosen metal. The formula is Weight = Volume x Density. Volume depends on the cross-sectional area of the chosen shape times the length for bars, tubes and pipes. For a round bar the area is pi x r^2, for a square bar it is side^2, for a hex bar it is (sqrt(3)/2) x across-flats^2, for a hollow pipe it is pi x (outer-radius^2 minus inner-radius^2), and for a flat plate it is width x thickness. A sphere has volume (4/3) x pi x r^3, which does not involve a length. Multiply any of these volumes by the metal density in kg/m³ and you have the mass in kilograms.
Choosing the right shape and why it matters
Structural profiles differ enormously in how much steel or aluminium they contain per metre of length. A 50 mm solid round bar contains roughly four times the steel of a 50 mm pipe with a 4 mm wall, so the shape selection has a far bigger impact on cost and weight than the choice of alloy grade. Hollow sections, tubes and pipes are engineered specifically to deliver high stiffness for low weight: an I-beam or square tube has far more bending resistance per kilogram than a solid bar of the same cross-sectional area. When planning a project, compare the weight of alternative profiles before ordering.
Metal densities and how to use a custom value
Density is the key input that links geometry to mass. The values in this calculator come from MatWeb and ASM International material databases, and are typical figures for standard commercial grades. Actual density can vary by a percent or two depending on the precise alloy composition, heat treatment and test method, so for precision engineering work always check your supplier or mill certificate. If you have a specific density, select "Custom density" from the material list and enter your value in kg/m³. The calculator will use it immediately.
Unit conversions and cost estimates
Switch between millimetres, metres, inches and feet for dimensions, and between kilograms, grams, metric tonnes, pounds and ounces for the result. Enter a price per kilogram to get an instant material cost estimate for the full batch. The cost is always calculated from the kilogram mass regardless of which weight output unit you have chosen, so you can display pounds in the result while pricing in kg without any manual conversion.
Metal densities - quick reference
| Metal / alloy | Density (kg/m³) | Relative to steel |
|---|---|---|
| Tungsten | 19300 | 2.46x |
| Gold | 19320 | 2.46x |
| Platinum | 21450 | 2.73x |
| Lead | 11340 | 1.45x |
| Silver | 10490 | 1.34x |
| Copper | 8960 | 1.14x |
| Nickel | 8908 | 1.14x |
| Bronze | 8800 | 1.12x |
| Brass | 8500 | 1.08x |
| Stainless steel 304/316 | 8000 | 1.02x |
| Steel (carbon) | 7850 | 1.00x |
| Iron (wrought) | 7874 | 1.00x |
| Cast iron | 7200 | 0.92x |
| Zinc | 7133 | 0.91x |
| Chromium | 7190 | 0.92x |
| Tin | 7287 | 0.93x |
| Molybdenum | 10220 | 1.30x |
| Cobalt | 8900 | 1.13x |
| Titanium | 4510 | 0.57x |
| Magnesium | 1738 | 0.22x |
| Aluminium (general) | 2700 | 0.34x |
| Aluminium 7075 | 2810 | 0.36x |
Densities sourced from MatWeb and ASM International. Values are nominal and may vary by alloy temper and heat treatment.
Frequently asked questions
How do I calculate the weight of a steel bar?
For a round steel bar, the weight is: pi x (diameter / 2)^2 x length x density. For steel the density is about 7850 kg/m³. A 50 mm diameter round bar 1 metre long weighs pi x 0.025^2 x 1 x 7850 = about 15.4 kg. Use this calculator to handle any shape and unit combination automatically.
Why does the calculator ask for wall thickness for pipes and tubes?
Pipes and tubes are hollow profiles. The weight comes only from the material in the wall, not the empty space inside. The formula subtracts the volume of the hole from the volume of a solid cylinder (or square), so the wall thickness determines how much material is present. A thicker wall means more weight per metre.
How accurate are the density values?
The densities are nominal figures sourced from MatWeb and ASM International, cross-checked against standard engineering tables. They are accurate to within 1 to 2 percent for most commercial grades, which is sufficient for estimating shipping weight, loading calculations and material cost budgets. For critical applications use the certified density from your supplier's material certificate.
What is the across-flats measurement for a hex bar?
Across flats (AF or A/F) is the distance measured directly between two parallel flat faces of a hexagonal bar. It is the same as the wrench or spanner size. The cross-sectional area of a regular hexagon is (sqrt(3)/2) x AF^2, which is what the calculator uses. Do not confuse it with the corner-to-corner diagonal, which is larger by a factor of 2/sqrt(3) or about 1.155.
Can I calculate the weight of multiple pieces at once?
Yes. Enter the number of pieces in the "Number of pieces" field and the calculator shows both the per-piece weight and the total weight for the batch. If you also enter a price per kg, the cost estimate covers the entire batch.
How do I convert kg/m³ to lb/in³?
Divide by 27,679.9. For example, steel at 7850 kg/m³ is 7850 / 27679.9 = 0.2836 lb/in³. You can also enter your dimensions in inches and select pounds as the weight unit; the calculator converts internally.