How to buy aluminium: lengths, kilos and kg/m
Profiles are sold by the length and priced by the kilo. To avoid overpaying or running short, there is one number you need to know: the weight per metre.
In short
- In Argentina, profiles are sold in 6-metre lengths and the price is usually given per kilo.
- The key number is the kg/m: weight per length = kg/m × 6; order weight = weight per length × number of lengths.
- The kg/m comes from the cross-sectional area: each mm² weighs 0.0027 kg per metre.
6-metre lengths
In Argentina, profiles are sold in 6-metre lengths. They can be ordered cut, but the material is counted in full lengths. Distributors publish the price per kilo or per length, depending on the product and the finish.
The key number: kg/m
Every profile has a weight per metre (kg/m), which is listed in the catalogues. Everything else follows from it:
Weight per length = kg/m × 6
Order weight = weight per length × number of lengths
Example: a 60 × 40 × 2 mm rectangular tube weighs 1.04 kg/m. One length weighs 1.04 × 6 = 6.2 kg, and 20 lengths weigh 124 kg.
Where the kg/m comes from
The weight per metre is the cross-sectional area multiplied by the density of aluminium. With 2.70 g/cm³:
kg/m = cross-sectional area (mm²) × 0.0027
The tube in the example has a cross-section of 384 mm²: 384 × 0.0027 = 1.04 kg/m.
The other way round: I have kilos, how many lengths is that?
If you have a budget or a stock in kilos, divide by the weight of one length and keep only the whole lengths: 100 kg of that tube is 16 lengths (99.5 kg), because a 17th length would no longer fit.
And watch the price per kilo: a profile that is lighter per metre costs less per length, even if the price per kilo is the same.
Frequently asked questions
How much does a 6-metre length of aluminium profile weigh?
It depends on the profile: it is its weight per metre multiplied by 6. A 60 × 40 × 2 mm tube weighs about 6.2 kg per length.
How do you calculate the weight of an aluminium profile?
Multiply the cross-sectional area in mm² by 0.0027 to get the weight in kg per metre.
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