Aluminum Weight Calculator

Aluminum is ordered by size but paid for by weight, and the gap between the two is widest on exactly the pieces people ask about: plate, bar, tube, wire and can stock. This page closes that gap for eleven stock shapes. Pick the alloy, pick the shape, type the dimensions you measured, and it returns the mass of one piece or of the whole batch.

Three jobs bring people here, and all three use the same screen:

• Weigh stock before you handle it. A plate, a bar or a length of tube, in kilograms or pounds, before it is picked up, loaded or booked onto a van.
• Price a batch instead of a piece. Set the number of pieces and the result is the total mass, which is the figure a freight quote or a scrap ticket asks for.
• Go the other way. Start from a target mass and let a dimension or the piece count be solved for. That is how a job that says “45 kg of 50 mm tube” turns into an actual cut length.

The alloy menu supplies the density, so you never have to look a material constant up separately. Each dimension carries its own unit menu, so a length in feet and a thickness in millimetres can be entered side by side without converting anything by hand, and the answer can be shown in grams, kilograms, ounces, pounds, stones or tons.

One plate, two pieces

Take a 6063 plate — 2700 kg/m³, the same nominal density as the average aluminum entry — that measures 1 m by 50 cm and is 10 mm thick, in two pieces. Enter the thickness as 10 mm and the other two in metres, then set the count to 2:

That is 13.5 kg per plate, and 27 kg for the pair — about 59.5 lb, which the result box will show if its unit menu is switched to pounds. The mass on screen always belongs to the whole batch, so check the count before quoting a number.

Every shape answers the same one-line question:

where $W$ is the mass of the batch, $V$ is the volume of one piece, $\rho$ is the alloy density and $n$ is the number of identical pieces. Only the volume changes from one shape to the next:

The can is the one shape with two parts, and the two parts are weighed differently. The wall is a hollow cylinder, the wall thickness is the difference between the two radii, and the base is a solid disc of the inner radius over the base height:

A lid is a full disc of the outer radius, laid on top of that:

The same statement, read backwards

Because the mass, the density and the count are one product, any single unknown can be recovered from the rest:

• A missing volume or a target mass: $V = W / (\rho\,n)$.
• A missing dimension, once the volume is known. The plate divides (its length is $L = V / (w\,t)$); the circular prism, hexagonal prism, octagonal prism, ring prism and wire take a square root, such as $r = \sqrt{V / (\pi L)}$ for the wire; the sphere takes a cube root, $r = \sqrt[3]{3V / (4\pi)}$.
• The count itself: $n = W / (\rho\,V)$, which answers how many pieces make up a given mass.
• The density is deliberately not one of them. It is a property of the alloy you selected, so the Density row is read-only and follows the Alloy menu.

Every entry is normalised before it multiplies

The multiplication needs one scale, so each entry is converted first: lengths to metres, volumes to cubic metres, density to kilograms per cubic meter and the result to kilograms, before it is shown in whichever mass unit is selected.

The imperial factors are exact definitions rather than rounded table values: an inch is 0.0254 m, the international foot is 0.3048 m and the avoirdupois pound is 0.45359237 kg, which is why a conversion never introduces an error of its own. The inch, foot and yard definitions are set out in the NIST Guide to the SI, Appendix B.

Fourteen entries sit in the Alloy menu. The differences look small in absolute terms — the whole menu spans 2600 to 2800 kg/m³ — but they are real, and they move the answer by the same percentage as the density moves.

The spread is worth paying attention to when the mass itself is the deliverable. The lightest wrought entry, 5083 at 2650 kg/m³, and the heaviest, 7075 at 2800 kg/m³, differ by about$\,5.7\%$, so the same plate weighs five or six percent more in one than in the other. Guessing the alloy is fine for a rough handling figure and less fine for a freight booking.

The values are nominal figures for each designation, not a measurement of your piece. Real stock varies with the exact composition within the grade specification, with temper, and with the thickness and width tolerances the mill rolls to. Treat a result as typical for that alloy rather than certified for the bar in your hand.

Two entries deserve a word. Melted aluminum at 2600 kg/m³ is liquid metal, so it is there for melt and casting estimates, not for a solid billet.Aluminum (average) is the right fallback when the grade is unknown: it is the value the menu opens on, and it sits in the middle of the range.

The Density row is read-only because the alloy owns it, but its unit menu still works: switch it to g/cm³, lb/ft³ or lb/in³ and the same density is re-expressed. If your datasheet quotes a scale that is not in that menu, convert it first with the density conversion calculator.

Type a target mass into the result box and the page solves for whatever else is still free. Which box gives way follows a simple rule, and knowing the rule saves a lot of retyping.

• Numbers you typed win. A dimension, count or mass you entered is treated as a measurement you are sure of.
• The count gives way first. Until you set the count yourself it is the default of one, so it is the first quantity to be solved, and the answer reads “this is how many pieces reach that mass”.
• Then the first dimension of the shape. For a plate that is the length, for round bar the radius, for a tube the length, for a can the wall height.

A target mass on the plate from above

Start from a 1 m × 0.5 m plate, 10 mm thick, at 2700 kg/m³ — one piece weighs 13.5 kg — and ask for 27 kg. The plate dimensions are measurements, so the count is what changes: two pieces. Fix the count at three instead, and the length becomes the answer:

Every mass, count and dimension that results from a target is marked as a solved value while you work, so you can tell your own figures from the ones the page supplied.

A cut length of tube

A 50 mm outside diameter tube with a 2 mm wall weighs 0.8143 kg per metre. Pin the count at one, then ask for 1 kg: the length comes back as 1.228 m, which is the number to set on the saw. Leaving the count on its default would have answered a different question — how many one-metre lengths weigh 1 kg.

Where the ring is different

The torus volume is a cubic in either radius, so the ring does not offer a radius solution from a target mass. The count absorbs the target instead: 5 kg of rings that weigh 2.498 kg each comes back as 2.001 pieces. Read that as “two rings are 4.996 kg, and you need a third to reach 5 kg” rather than as a fraction of a ring, and round the count up for an order.

A target that the geometry cannot reach is not silently rounded. Give a ring prism with a 2 cm outer radius and a 10 mm thickness a 100 kg target and the bore stays blank with an explanation, because no bore would make a disc of that diameter and thickness weigh 100 kg. In the same way, a bore wider than the outside turns both radius boxes red while leaving the numbers visible, so an impossible measurement is flagged rather than hidden.

• The diameter and side-length boxes have no millimetre entry. Those rows use the general length menu, which runs centimetres, decimetres, metres, inches, feet, yards, feet plus inches, and metres plus centimetres. A 50 mm outside diameter is 5 cm, and a 0.0254 m diameter is exactly one inch. If you are converting a millimetre drawing, the length converter is quicker than doing it in your head.
• The Thickness box opens in metres. Sheet is normally quoted in millimetres, so switch that row to millimetres and type 3, not 0.003. A thickness entered on the wrong scale is an easy way to be out by a factor of a thousand.
• A mil is a thousandth of an inch. It is 0.0254 mm, not one millimetre — the two units in that menu are a factor of 39 apart. If the drawing gives mils, enter mils; a millimetre figure belongs on the millimetre entry.
• Round and polygonal shapes take a radius, not a diameter — and a side, not a width across the flats. The hexagonal prism wants the length of one side of the hexagon; across the flats that is $\sqrt{3}\,s$, so a bar measuring 20 mm across the flats has an 11.55 mm side. The octagon follows $\left(1+\sqrt{2}\right)s$ instead. The tube is the exception: it carries both diameters and both radii and keeps them in step, so either one can be filled in first.
• Measure the piece, not the label. Mill tolerances are small in absolute terms and large in relative terms. On 3 mm sheet, half a millimetre is$\,17\%$ of the mass, while the same error on 50 mm plate is one percent. Calipers on the actual sheet are worth more than a datasheet thickness.
• Count identical pieces only. The multiplier applies to one shape at a time. For a mixed batch, calculate each shape separately and add the results, or use the Other prisms route with the combined material volume.

For a solid rectangular block of any other material, the size to weight calculator takes the same three dimensions with a density you supply and works in both directions.