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Metal Weight Calculator

Work out what a piece of steel, aluminium, stainless or brass weighs from its shape and dimensions, per foot and per piece, with cost and a material comparison.

How to use this calculator

  1. 1Pick the shape first - the dimension fields change to match it, and the labels tell you which measurement each one wants.
  2. 2For a hexagon, enter the across-the-flats size, which is what a spanner reads and what the stock is sold by.
  3. 3For plate, the first dimension is the width, the second is the thickness, and the length is the other in-plane dimension.
  4. 4Set the payload figure if you are collecting the material. Steel reaches a payload long before it fills a truck bed.

How the calculation works

Weight = cross-sectional area x length x density Round bar: pi r^2 Square bar: s^2 Hexagon: (sqrt(3) / 2) F^2 Tube: outside area - inside area, inside = outside - 2 x wall Angle: (leg A + leg B - thickness) x thickness
Density
Pounds per cubic inch. Mild steel 0.2836, stainless 304 0.289, aluminium 6061 0.0975, brass 0.307, copper 0.323
F
Across-the-flats distance of a hexagon - the size a spanner reads, not the corner-to-corner diagonal
Angle
Two legs meeting at a corner. The thickness is subtracted once so the shared corner is not counted twice

All the carbon steels - A36, 1018, 1020, A572 - are close enough to 0.2836 lb per cubic inch that the difference between them never matters in practice. The families that differ are aluminium at about a third, and copper and brass at rather more than steel.

Plate and sheet are usually quoted per square foot rather than per foot of length, because they are bought by area. A quarter-inch steel plate is 10.2 lb per square foot, and every other thickness scales linearly from that.

Structural shapes - I-beams, channels, wide flange - are specified by their weight per foot rather than calculated from dimensions, because their fillets and tapers make the true section awkward. A W12x26 is 26 lb per foot by definition.

Worked example

A sheet of quarter-inch steel plate

  1. 1.A 4 by 8 ft sheet is 48 by 96 in, at 0.25 in thick.
  2. 2.Cross-section is 48 x 0.25 = 12 sq in, and over 96 in of length that is 1,152 cubic inches of steel.
  3. 3.At 0.2836 lb per cubic inch that is 326.7 lb.
  4. 4.Which is also 10.21 lb per square foot times 32 square feet - the standard figure for quarter-inch plate, arrived at the other way round.

Result: About 327 lb - a fifth of a half-ton pickup, from one sheet

Twenty feet of 2 x 2 x 1/4 angle

  1. 1.An angle is two legs sharing a corner, so the area is (2 + 2 - 0.25) x 0.25 = 0.9375 sq in.
  2. 2.Adding the two legs without subtracting the thickness would give 1.0 sq in - nearly 7% high, because the corner would be counted twice.
  3. 3.Per foot that is 0.9375 x 12 x 0.2836 = 3.19 lb, which is the published figure for 2 x 2 x 1/4 angle.
  4. 4.Over 20 ft, 63.8 lb.

Result: 3.19 lb/ft, 63.8 lb for the stick

The same bracket in aluminium

  1. 1.A 2 x 3 in rectangular tube with a 1/8 in wall: outside area 6 sq in, inside 1.75 x 2.75 = 4.8125, so 1.1875 sq in of metal.
  2. 2.Only 20% of the envelope is material, which is what tube is for - the removed middle contributes almost nothing to bending stiffness.
  3. 3.In 6061 at 0.0975 lb per cubic inch, a 36 in length is 4.17 lb; four of them 16.7 lb.
  4. 4.The same four in mild steel would be 48.5 lb - close to three times as much, which is the density ratio and nothing else.

Result: 4.17 lb each, against 12.1 lb in steel

Why the section matters more than the size

Two pieces of steel with the same outside dimensions can differ in weight by a factor of five, and it is entirely down to how much of the envelope is actually metal. A solid 2 inch square bar is 4 square inches of section; a 2 inch square tube with an eighth-inch wall is under one.

What makes that trade worth taking is that bending stiffness does not come from the middle. The second moment of area weights every element by the square of its distance from the neutral axis, so material near the centre contributes almost nothing. Removing it costs a small fraction of the stiffness and a large fraction of the weight, which is why tube, I-beams and hollow sections dominate structural work.

It also explains why substituting a solid bar for a tube of the same outside size is nearly always the wrong instinct. It quadruples the weight to buy a modest increase in stiffness, and it costs several times as much.

Density across the common metals

Within a family, density barely varies. Every carbon steel worth naming - A36, 1018, 1020, 4140, A572 - sits close enough to 0.2836 pounds per cubic inch that the difference never affects an estimate. The alloying that separates them is measured in fractions of a percent by weight.

Across families the differences are large and structural. Aluminium is about a third of steel; titanium a little over half; copper and brass a little more than steel; lead nearly half again more. Those ratios drive most material substitutions, and the one that gets misread is aluminium, because its stiffness falls in almost exactly the same proportion as its density.

That last point is worth stating plainly. Swapping a steel part for an aluminium one of identical dimensions cuts the weight by two thirds and cuts the stiffness by two thirds as well - the part will flex three times as far under the same load. Aluminium wins on weight only when the section is allowed to grow, which is why aluminium extrusions are so much chunkier than their steel equivalents.

  • Mild steel, 0.2836 — The reference. Every carbon steel is within a rounding error of this.
  • Stainless 304, 0.289 — About 2% heavier than carbon steel, and considerably more expensive.
  • Aluminium 6061, 0.0975 — Roughly a third of steel by weight - and by stiffness.
  • Brass, 0.307 / copper, 0.323 — Heavier than steel. A copper busbar weighs more than the steel it replaces.
  • Titanium, 0.160 — Between aluminium and steel, with steel-like strength. The price is why it is not everywhere.

Where calculated weight and delivered weight part company

Mill tolerance is the first and largest gap. Hot-rolled plate is permitted to vary from its nominal thickness, and the permitted variation is not symmetric - the standards allow noticeably more over than under, because a mill that runs light is shipping less than it billed. A stack of quarter-inch plate therefore tends to weigh a little more than the nominal calculation says, consistently.

Second is that structural shapes are not calculated at all. A W12x26 weighs 26 pounds per foot because that is its designation; the actual section has root fillets and flange tapers that no simple formula captures. The same is true of channels, and of most standard angles once you get away from equal legs and square corners. For those, the published weight per foot is the number, and calculating from the dimensions will be close but not right.

Third is coatings. Galvanising adds real weight - enough that galvanised sheet gauge is a different standard from bare sheet gauge specifically to account for it. And a heavy paint system on a large fabrication is not nothing either, though it rarely changes a decision.

What this assumes, and where it stops

Assumptions

  • Densities are standard published values for the common alloys at room temperature.
  • Cross-sections are exact geometric shapes - square corners, uniform walls, no fillets or radii.
  • Nominal dimensions are used, with no allowance for mill tolerance, which in practice tends to run over rather than under.
  • Coatings are not included. Galvanising in particular adds measurable weight.

Limitations

  • Structural shapes - wide flange, S-beams, channels, and most standard angles - are defined by their published weight per foot, not by their nominal dimensions. Calculating from dimensions will be close and not exact.
  • It does not model fillets, radii, chamfers, holes or cutouts. Any of those change the weight of a real part.
  • Pipe sized by NPS and schedule does not have an outside diameter equal to its nominal size. Use the actual measured outside diameter and wall thickness.
  • Cast and sintered parts vary in density with porosity, so a casting can come out several percent off a solid-material calculation.
  • Weight is not the same question as strength or stiffness. A lighter material is not automatically a worse one, or a better one.

Common questions

How much does a sheet of steel weigh?

Multiply the square footage by 10.2 pounds for every quarter inch of thickness - so a 4 by 8 sheet of quarter-inch plate is 32 square feet at 10.2, which is 327 pounds. Eighth-inch is half that, half-inch double. The underlying figure is 40.8 pounds per square foot per inch of thickness for steel.

Is aluminium a third the weight of steel?

Almost exactly - 0.0975 pounds per cubic inch against 0.2836, so 34%. The catch is that its stiffness falls by nearly the same proportion, so an identical part in aluminium flexes about three times as much. Aluminium saves weight when the design is allowed to use a bigger section, which is why aluminium parts look chunky next to the steel ones they replaced.

Why does my calculated beam weight not match the catalogue?

Because structural shapes are defined by their weight rather than by their nominal dimensions. A W12x26 is 26 pounds per foot by designation, and its real section has root fillets and tapered flanges that a rectangle-and-triangle calculation cannot capture. For standard shapes, use the published figure.

How do I work out the weight of hexagon bar?

Area is the square root of three, over two, times the across-flats dimension squared - about 0.866 F squared. A one-inch hex bar is 0.866 square inches, so 2.95 pounds per foot in steel. Treating the across-flats measurement as a diameter and using pi r squared gives 0.785 square inches, which is 10% low.

Does the calculated weight include the galvanising?

No. Galvanising adds a real and measurable amount - enough that the sheet metal industry maintains a separate galvanised gauge standard whose thicknesses include the coating. For hot-dip work on structural steel the addition is usually in the range of a few percent, and it is worth allowing for on a large fabrication.

Sources

Formula and content last reviewed on .

Results are estimates for information only, not professional advice.

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