The formulas (dimensions in mm, result in kg/m)
Flat = Width × Thickness × 0.00785
Round = Diameter² ÷ 162
All three come from the same source: mild steel's density of 7,850 kg/m³ applied to the bar's cross-sectional area. The constant 0.00785 is that density expressed as kg per mm² of cross-section per metre of length; the round-bar shortcut (÷162) is the same formula used in the Rebar Weight calculator, since a rebar is just a round bar.
Frequently asked questions
Is the round bar formula the same as the rebar calculator?
Yes — a round mild steel bar and a plain reinforcement bar have the same cross-section-based weight formula (diameter² ÷ 162). Ribbed/deformed rebar uses the same nominal-diameter formula in standard steel tables.
What steel density does this assume?
7,850 kg/m³ — the standard reference density for mild/carbon steel used across steel mill weight tables.
Does bar shape affect strength, not just weight?
Yes, though that's outside this calculator's scope — it only computes weight from geometry. Section modulus and strength depend on the shape and orientation of loading, which you'd check against a structural reference or your engineer's spec.