Structural Steel & Metal
Angle Iron Weight Calculator
Calculates the weight and cost of steel angle iron by size, length, and quantity
Updated 27 May 2026 · Live
What this tool does
Calculates the weight of steel equal-angle (L-section) from leg size, thickness, length, and quantity, with an indicative material cost.
Formula Used
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How the angle iron weight calculator works
The calculator works out the weight of steel equal-angle (L-section) from its leg size, thickness, length, and quantity, then multiplies by a price per kilogram for an indicative material cost. The cross-sectional area of an equal angle is taken as (2a − t) × t, where a is the leg length and t the thickness; multiplying by the steel density (7,850 kg/m³) gives the mass per metre, and multiplying that by the length and the number of pieces gives the total weight. Every figure recalculates from the values entered.
The simplified cross-section formula
The area term (2a − t) × t treats the angle as two rectangles meeting at the heel, with the overlap counted once. It ignores the rolling radii at the inner corner (the root) and the leg tips (the toes). Those radii add a small amount of metal, so the published section masses in BS 4 and BS EN 10056 run roughly 1% heavier than this formula. For a 50 × 50 × 5 equal angle the simplified figure is about 3.73 kg/m against a published 3.77 kg/m. The difference is immaterial for ordering and budgeting, while a precise structural take-off references the published section mass.
What angle iron is
"Angle iron" is the trade name for hot-rolled steel angle — an L-shaped section with two legs at 90°. An equal angle (EA) has both legs the same length; an unequal angle (UA) does not. Sections are described as leg × leg × thickness in millimetres, so 50 × 50 × 5 EA has two 50 mm legs and a 5 mm wall. This calculator covers equal angles; the area term differs for unequal angles.
Worked example
A 50 × 50 × 5 equal angle, 3 m long, one length: area = (2 × 50 − 5) × 5 = 475 mm². Mass per metre = 475 ÷ 1,000,000 × 7,850 = 3.73 kg/m. Total = 3.73 × 3 = 11.2 kg. At £2.10/kg the indicative material cost is about £23.49. A quantity of four lengths multiplies both the weight and the cost by four.
Common equal-angle sizes
UK stockholders carry a standard range of equal angles, typically from 20 × 20 × 3 up to 200 × 200 × 24, with 50 × 50 × 5, 60 × 60 × 6, 75 × 75 × 8, and 100 × 100 × 10 among the most common for general fabrication, brackets, frames, and lintels. Heavier sections carry more load and weigh proportionally more to handle and transport. The leg and thickness inputs accept any value in range, so non-standard sizes can be entered directly.
Steel density and grade
The calculation uses 7,850 kg/m³, the standard density for structural carbon steel — grades S235, S275, and S355 to BS EN 10025 all sit within a fraction of a percent of this. Grade governs strength rather than weight, so the same section weighs the same whether it is S275 or S355.
Why there is no wastage field
Structural steel angle is cut to length at the stockholder or mill, so off-cut wastage on delivered lengths is effectively nil — unlike sheet or board materials. Fabrication offcuts and drilling swarf sit with the fabricator rather than being a quantity the buyer adds, so this tool reports the net weight of the sections specified, with no wastage allowance.
Reading the results
The primary figure is the total weight of all the lengths entered. The breakdown shows the section designation, the mass per metre, the length of each piece, the weight of a single length, and the indicative material cost. Separating per-length weight from the total shows how an order scales: doubling the quantity doubles the weight and the cost, while the mass per metre stays fixed for a given section.
Structural design and Building Regulations
Structural steel elements are designed by a chartered structural engineer working to BS EN 1993 (Eurocode 3); a weight figure is not a design check. In England and Wales structural work falls under Approved Document A of the Building Regulations, and fire protection of steel — intumescent coating, boarding, or encasement — falls under Approved Document B. A pre-application enquiry to the local authority gives early clarity on what a particular project needs, and tends to cost less than retrospective correction.
Corrosion protection and finish
Steel for internal use is commonly supplied pre-primed, for example with a single coat of zinc-phosphate primer, and any intumescent or decorative top-coat follows later. Steel exposed to weather is usually hot-dip galvanised. Galvanising adds a thin zinc layer — typically under 1% of the section weight — which this calculator does not include.
Using this alongside other BuildMetricLab tools
Weight drives haulage and handling, so the figure here pairs with the steel I-beam, hollow-section, and steel-plate weight calculators for a fuller take-off, and with the material-cost and project-budget tools for an overall estimate. Every BuildMetricLab tool runs entirely in your browser — no sign-up, no data sent anywhere, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Weight = (2a − t) × t × ρ × L × q, where a is the leg length, t the thickness, ρ the steel density (7,850 kg/m³), L the length per piece, and q the quantity. The cross-section term (2a − t) × t is the simplified equal-angle area; it excludes the root and toe radii, so the result reads roughly 1% lighter than the published section masses in BS 4 / BS EN 10056 (about 3.73 vs 3.77 kg/m for a 50 × 50 × 5 angle). Material cost = total weight × price per kg. Every result is computed from the values entered.
Frequently asked questions
How accurate is the calculated weight?
The cross-section formula (2a − t) × t omits the rolling radii at the root and toes, so it reads about 1% lighter than the published section mass in BS 4 and BS EN 10056 — for a 50 × 50 × 5 angle, roughly 3.73 kg/m against a published 3.77 kg/m. That is close enough for ordering and budgeting, while a precise structural take-off uses the published section mass.
Does the quantity field change the total?
Yes. The weight and the indicative cost cover all the lengths entered. The breakdown also shows the weight of a single length and the mass per metre, so the per-piece and total figures are both visible.
Does steel grade affect the weight?
No. Structural steel grades such as S235, S275, and S355 share essentially the same density, about 7,850 kg/m³, so a section's weight is the same regardless of grade. Grade affects strength, not mass.
Does this replace professional advice?
No. This is a quantity and cost estimator. Sizing a structural member, checking deflection, or confirming fire protection is the work of a chartered structural engineer to BS EN 1993 and the Building Regulations.
Can I change the price per kilogram?
Yes — the price per kg is editable, so entering a current stockholder figure gives a total that matches a specific quote. Steel prices move with the market, so a recent figure gives the most realistic cost.
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