FRP vs steel weight
See exactly how much lighter pultruded FRP is than steel for the same section. Pick a shape, and Dimviz reweighs the identical geometry in FRP and in steel from their densities — so the weight saving is exact, not a rule of thumb.
FRP is about 4× lighter than steel: pultruded FRP is ~1900 kg/m³ versus ~7850 kg/m³ for steel — roughly a 76% 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.
Why FRP is so much lighter
Weight per metre is cross-sectional area × density, and the area is fixed by the geometry — so swapping steel for FRP scales the weight by the density ratio alone. Pultruded E-glass FRP sits around 1900 kg/m³ against structural steel's 7850 kg/m³, a factor of about 4.1. That's why an FRP handrail, walkway or ladder can be carried and installed by hand where the steel equivalent needs lifting gear.
Weight saving isn't the whole story
FRP wins decisively on mass and on corrosion (no paint, no galvanising, no rust), but steel is far stiffer — its elastic modulus is roughly 10× that of FRP — so FRP sections are sized by deflection, not strength, and are often deeper than the steel they replace. Compare the section properties, not just the weight, before you swap. Dimviz reports both from the same geometry.
FAQ
How much lighter is FRP than steel?+
About 4× lighter. Pultruded FRP is roughly 1900 kg/m³ and steel roughly 7850 kg/m³, so for the same section FRP weighs about 24% of the steel — a ~76% weight saving.
Does FRP replace steel one-for-one?+
Not always. FRP is much lighter and corrosion-free, but far less stiff, so a like-for-like swap may deflect too much. Sections are usually resized (often deeper) and checked against a deflection limit like L/180.
Is the comparison exact?+
Yes for weight — it's the exact density ratio applied to the real section area. Stiffness and strength depend on the FRP grade and must be checked separately.