Aluminium vs steel weight
See exactly how much lighter aluminium is than steel for the same section. Pick a shape, and Dimviz reweighs the identical geometry in 6063 aluminium and in steel from their densities — so the weight saving is exact, to the kg/m.
Aluminium is about 2.9× lighter than steel: 6063 aluminium is ~2700 kg/m³ versus ~7850 kg/m³ for steel — roughly a 66% weight saving for the same cross-section.
Weight per metre = cross-sectional area × density. Area is the same for both materials, so the ratio is exactly the density ratio — independent of which section you pick. Figures computed from the section geometry.
How the weight saving works
Because weight per metre is area × density and the area is set by the section, swapping steel for aluminium scales the weight by the density ratio. Aluminium 6063 is about 2700 kg/m³ against steel's 7850, a factor of roughly 2.9 — so the aluminium extrusion weighs about a third of the steel section, before any redesign.
Stiffness and redesign
Aluminium's elastic modulus is about a third of steel's, so a direct swap of the same section deflects roughly three times as much. In practice aluminium members are resized — thicker walls or a deeper profile — which claws back some of the raw weight saving. Compare the section properties (Ix, Sx) alongside weight to size the replacement properly.
FAQ
How much lighter is aluminium than steel?+
About 2.9× lighter. Aluminium is roughly 2700 kg/m³ and steel roughly 7850 kg/m³, so the same section in aluminium weighs about 34% of the steel — a ~66% weight saving.
Can I use the same section in aluminium?+
Geometrically yes, but aluminium is about a third as stiff, so the same section deflects ~3× as much. Members are usually resized and rechecked against a deflection limit.
What aluminium density is used?+
2700 kg/m³, typical of 6063 extrusion alloy. Switch the material in the tool to compare stainless, copper or FRP against steel too.