Introduction
A steel angle — the familiar L-shaped bar of structural steel — looks simple, but its weight per foot (or per meter) is the number that drives almost every decision around it: how much to order, what the freight bill will be, whether a crew can hand-carry a length, and how much dead load lands on a structure.
The Steel Angle Weight Calculator turns leg dimensions, thickness, and length into a weight you can act on — in pounds per foot and kilograms per meter, plus total weight for your pieces. This guide explains everything behind that number: how angle sizes are read, the formula the calculator uses, a fully worked example checked in both unit systems, and the judgment calls the calculator can’t make for you.
What a Steel Angle Is and Where It’s Used
A steel angle is a hot-rolled structural section whose cross-section is an “L”: two legs at 90 degrees. The legs can be equal length (a equal-leg angle, e.g., L3×3×1/4) or different lengths (unequal-leg angle, e.g., L4×3×1/4). The designation reads as: long leg × short leg × thickness — all in inches in the US convention.
Angles show up in more places than most people realize: structural bracing (cross-bracing in steel frames, tower bracing, roof trusses), lintels supporting brick or block over window and door openings, equipment and machine frames for platforms and skids, shelving and rack brackets, and miscellaneous steel — stair stringers, sign posts, trailer frames, and edge protection.
Weight matters in all of these for three reasons: ordering (steel is priced by weight, typically per ton/tonne), handling (a 20-ft length of heavy angle is not a one-person lift), and shipping (freight is quoted on weight and dimensions, and truckloads have hard limits). If you’re pricing the material itself, pair this guide with the cost guide, which walks through price-per-ton estimating.
Reading an Angle Designation
US structural angles are designated by leg lengths and thickness in inches: L4×4×1/2 has 4-inch legs and 1/2-inch thickness; L6×3-1/2×5/16 has 6-inch and 3-1/2-inch legs, 5/16-inch thick.
Three inputs determine the weight: leg length(s), thickness, and the steel density — 490 lb/ft³ (7,850 kg/m³) for carbon steel. One nuance: the simple cross-section formula slightly overstates weight versus published mill tables (which account for toe and fillet radii), so treat calculated weights as planning figures and verify against ASTM A6 mill tables before final procurement — the material guide covers the grades and specs behind the numbers.
The Formulas Involved
The calculator runs a short chain: cross-section area from the legs and thickness, weight per unit length from the density, then total weight from the total length.
Formula 1: Cross-section area
Area ≈ (2 × leg − thickness) × thickness for equal-leg angles (all in inches, giving in²). This is the thin-wall approximation — it treats the angle as two rectangles minus the double-counted corner square. For unequal-leg angles, replace 2 × leg with (long leg + short leg).
Formula 2: Weight per foot
W (lb/ft) = 490 × Area (in²) ÷ 144. Dividing by 144 converts the density from per-cubic-foot to per-square-inch-of-section (144 in² = 1 ft²), so the result is pounds per linear foot.
Formula 3: Unit conversion and totals
kg/m = lb/ft × 1.4882. Total weight = W × total length; convert pounds to short tons (÷ 2,000) or kilograms to metric tonnes (÷ 1,000). The formula-explained guide derives each step in detail, including the unequal-leg case.
Standard Equal-Leg Sizes (ASTM A6 Reference Weights)
The table below gives published reference weights for common equal-leg angles. Use these for quick takeoffs; verify against your supplier’s mill tables for ordering.
| Size (in) | Weight (lb/ft) | Weight (kg/m) |
|---|---|---|
| L2×2×1/8 | 1.65 | 2.46 |
| L2×2×1/4 | 3.19 | 4.75 |
| L2×2×3/8 | 4.70 | 6.99 |
| L3×3×1/4 | 4.90 | 7.29 |
| L3×3×3/8 | 7.20 | 10.72 |
| L3×3×1/2 | 9.40 | 13.99 |
| L4×4×1/4 | 6.60 | 9.82 |
| L4×4×3/8 | 9.80 | 14.58 |
| L4×4×1/2 | 12.80 | 19.05 |
| L5×5×3/8 | 12.30 | 18.30 |
| L5×5×1/2 | 16.20 | 24.11 |
| L6×6×1/2 | 19.60 | 29.17 |
| L6×6×3/4 | 28.70 | 42.71 |
Angles are typically stocked in 20-ft (6.1 m) and 40-ft (12.2 m) mill lengths, so a takeoff usually starts by counting sticks, not feet.
Worked Example: From Size Callout to Bundle Weight
A small shop order: 10 pieces of L3×3×1/4 × 20 ft for equipment frames.
Step 1 — Weight per foot. Area = (2 × 3 − 0.25) × 0.25 = 1.4375 in². W = 490 × 1.4375 ÷ 144 = 4.89 lb/ft, matching the published 4.9 lb/ft reference.
Step 2 — Total length. 10 × 20 ft = 200 linear feet.
Step 3 — Total weight. 200 × 4.9 = 980 lb, or 980 ÷ 2,000 = 0.49 short tons.
Cross-check in metric. 200 ft = 60.96 m; 60.96 × 7.29 = 444.5 kg — and 980 ÷ 2.20462 = 444.5 kg, so the two systems agree exactly.
Practical takeaway: 980 lb is a half-ton order — small enough for a flatbed partial or a pickup with a trailer, but not a tailgate load. For a larger order, estimating full bundles and freight is covered in the estimating guide.
Mistakes That Distort Results
- Confusing leg size with thickness. L3×3×1/4 has 3-inch legs; the 1/4 is thickness. Swapping them changes the weight by an order of magnitude.
- Using nominal density wrong. Aluminum angles (165 lb/ft³) and stainless (499 lb/ft³) need their own densities — 490 is carbon steel.
- Forgetting cut waste. A parts list summing to exactly 20 ft per stick assumes perfect cuts. Add a small cutting allowance, especially for many short pieces.
- Ignoring the coating. Hot-dip galvanizing adds negligible weight but changes unit price and spec — put it on the order, not discovered at delivery.
- Treating the thin-wall formula as exact. It’s a planning approximation; published mill tables are the procurement reference.
A fuller catalogue of these traps is in the common mistakes guide.
Related Guides
- Steel Angle Weight Formula Explained — the area, density, and conversion math step by step.
- Steel Angle Cost Guide — turning pounds and kilograms into material budgets.
- Steel Angle Material Guide — ASTM A36 vs. other grades, galvanized vs. black steel.
- Steel Angle Estimating Guide — takeoffs, bundles, and linear-foot estimating.
- Steel Angle Weight FAQ — quick answers to the most asked questions.
- Pro Tips — ordering, handling, and freight advice from the trade.
Frequently Asked Questions
How much does an L3×3×1/4 angle weigh per foot?
4.9 lb/ft, or 7.29 kg/m. A standard 20-ft length weighs 98 lb (44.5 kg).
What is the formula for steel angle weight?
Weight per foot = 490 × cross-section area (in²) ÷ 144, where area ≈ (2 × leg − thickness) × thickness for equal-leg angles. Multiply by length for total weight; convert with kg/m = lb/ft × 1.4882.
How much does a 20-foot steel angle weigh?
It depends on size: a 20-ft L2×2×1/4 weighs 63.8 lb (28.9 kg); a 20-ft L4×4×1/2 weighs 256 lb (116 kg); a 20-ft L6×6×3/4 weighs 574 lb (260 kg). Always confirm the size’s published lb/ft first — guessing the designation is the costliest mistake on this page.
What is the difference between equal-leg and unequal-leg angles?
Equal-leg angles have identical legs (L4×4); unequal-leg angles have different leg lengths (L6×4). The weight formula is the same — use (long leg + short leg − thickness) × thickness for the unequal-leg area.
Should I use published tables or the formula for ordering?
The formula is fine for planning and takeoffs; use published ASTM A6 mill tables (or your supplier’s tables) for the final purchase order, since mill tolerances shift real weights slightly.
Get Your Number
Steel angle weight is simple arithmetic built on three inputs — leg size, thickness, and length — plus the density of carbon steel. The Steel Angle Weight Calculator does the arithmetic; your job is reading the size callout correctly and measuring your lengths. Plug in your designation, check the per-foot weight against the table above, and confirm final numbers with your supplier’s mill tables before you order.
Disclaimer: Calculator results are planning estimates based on the dimensions you enter. Actual weights vary with mill tolerances, coatings, and material specifications. Verify weights against published mill/ASTM tables and your supplier, and consult a licensed professional or your local building authority for structural or code-related decisions.
