Steel bar weight
Theoretical per-metre and total weight for round (0.00617 × d²), square (0.00785 × a²), flat (0.00785 × width × thickness) and hex (0.0068 × s²) steel sections, with a switch between handbook-rounded and exact coefficients and an editable density (7.93 for stainless).
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Weight result
Theoretical weight — the weighbridge usually settles it.
Enter the size to calculate the steel weight
Per metre: 0 · Total: 0 · Section area: 0
What this tool does
- Check a delivery against nominal sizes: compare theoretical weight with the weighbridge figure.
- Bar-bending schedules and budgets: total weight per diameter and length, ready for the material list.
- Compare sections: see how round, square and flat bars differ in mass per metre for the same duty.
Example
Input
40x5
Output
扁钢（宽 × 厚 40 × 5 mm）每米重量：1.57 kg/m 6 m 总重量：9.42 kg 截面面积：200 mm² 系数（手册取整）：0.00785 公式：0.00785 × 200 mm² × 6 m = 9.42 kg
A 20 mm round bar is 2.468 kg per metre (0.00617 × 400), so a 9 m bar weighs 22.212 kg.
Frequently asked questions
Where does 0.00617 come from?
It is π/4 × 7.85 ÷ 1000 rounded: section area πd²/4 in mm² times 7.85 g/cm³ divided by 1000 gives kg/m. The exact value is 0.0061654; steel weight tables (GB/T 702 and friends) print 0.00617. Tick “Use exact coefficients” to compare.
Does it work for rebar?
Yes — GB/T 1499.2 defines rebar theoretical weight with the round-bar formula on the nominal diameter (Φ12 is 0.888 kg/m); the ribs are folded into the nominal section. Measured weight may differ by ±4%–±6%.
Why do square and flat bars share a coefficient?
Both sections are rectangles, so the area is the product of two sides and the coefficient is simply the density conversion 0.00785. Square bars have equal sides; flat bars need width and thickness separately.
Which hex dimension do I enter?
The distance across flats s (the spanner size), not across corners. The area is √3/2 × s² and 0.0068 is the rounded value of √3/2 × 7.85 ÷ 1000.
How do I switch to stainless or aluminium?
Change the density: 7.93 for 304, 7.98 for 316L, 2.70 for aluminium, 8.50 for brass. The coefficient scales linearly with density; tick the exact-coefficient box when you need the unrounded value.
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