Steel Weight Calculator

The Steel Weight Calculator estimates the weight of a steel item from its shape and dimensions. It works for round, square, hexagonal, and flat bars, plate, round pipe, square and rectangular tube, and equal or unequal angles. Pick a material from the preset list — mild steel, stainless 304/316, alloy steel, tool steel, cast iron, aluminum, brass, or copper — or enter a custom density for unusual alloys. The calculator returns the per-piece weight, total weight for any quantity, total volume, surface area for paint estimates, linear weight per metre or foot for ordering by length, and an optional total cost when you enter a price per kilogram or pound.

Why the formula is simple

Every shape calculation comes back to the same idea: weight equals volume times density. Volume is the cross-section area multiplied by the length for bars, pipes, tubes, and angles, or length × width × thickness for a plate. The cross-section area is what changes between shapes:

• Round bar: \(A = \pi d^{2} / 4\)
• Square bar: \(A = a^{2}\)
• Hex bar (across-flats f): \(A = \tfrac{\sqrt{3}}{2} f^{2}\)
• Flat / Rectangular bar: \(A = w \times t\)
• Plate: \(V = L \times W \times t\)
• Round pipe (OD D, wall t): \(A = \pi (D^{2} - d^{2}) / 4\) where \(d = D - 2t\)
• Square tube: \(A = a^{2} - (a - 2t)^{2}\)
• Rectangular tube: \(A = a b - (a - 2t)(b - 2t)\)
• Angle (legs a, b, thickness t): \(A = t (a + b - t)\)

Densities used

How to use the calculator

1. Pick units — Metric (mm + m + kg) or Imperial (inch + ft + lb).
2. Pick a shape. The form only shows the dimensions used by that shape, so you can never enter a wrong field.
3. Enter the cross-section. A live SVG preview labels each dimension on the matching diagram so you cannot confuse across-flats with across-corners, or OD with ID.
4. Enter length and quantity. Length is for one piece; the calculator multiplies by the count.
5. Pick a material from the preset list, or choose Custom and type a density in kg/m³.
6. Optional: enter a price per kilogram or pound. The calculator returns total cost for the order.
7. Click Calculate. Read the per-piece and total weight, surface area, volume, and weight in every common unit at once.

Where this tool fits in

Common pitfalls

• Hex bar across-flats vs. across-corners. The wrench size is the across-flats dimension; the diameter that just contains the hex is across-corners. The calculator uses across-flats — same as the steel mill catalogue.
• Pipe schedule confusion. Schedule numbers (40, 80) tie to wall thickness, not OD. If you only know the schedule and the nominal pipe size, look up the actual OD and wall before entering them here.
• Stainless density. Stainless steel is denser than carbon steel by about 2%. For long stainless rails or large quantities the difference adds up.
• Plate sheets are sold by area. When ordering a single plate, divide your design weight by the plate's per-square-metre weight — the linear-weight value won't apply.

Frequently asked questions

How is steel weight calculated? Steel weight equals volume multiplied by density. Volume is the cross-section area multiplied by the length for bars and tubes, or length times width times thickness for plate. Mild steel density is 7850 kg per cubic metre or 0.2836 lb per cubic inch.

What is the density of steel? Mild and alloy steels sit at about 7850 kg per cubic metre. Stainless steel grades 304 and 316 are slightly heavier at about 8000 kg per cubic metre. Cast iron is lighter, around 7200 kg per cubic metre. Use the custom material option to enter any other density.

How accurate is the calculation? The volume formulas are exact for the named shape. The total weight is therefore as accurate as the dimensions you enter, the chosen density, and the assumption that the section is uniform along its length. Real mill products have tolerances of typically plus or minus 1 to 3 percent on weight.

Why does pipe wall thickness matter so much? Pipe weight depends on the difference between outside and inside cross-section areas, so wall thickness has a strong leverage effect. Doubling the wall thickness on a thin pipe can almost double its weight even though the outside diameter is unchanged.

Can I use this for stainless steel and aluminum? Yes. The shape formulas are identical for any solid metal. Pick stainless 304 or 316, aluminum 6061, brass, or copper from the material list to apply the correct density. For unusual grades use the custom material option.

What is linear weight and why do I need it? Linear weight is the weight of one metre or one foot of the section. Steel mills sell stock by the linear metre or foot, and structural drawings call out beam sizes by linear weight, so the value is useful when comparing or ordering material.