Whether you're pricing a PEB structure, ordering rebar, or estimating a fabrication job, getting steel weight right the first time saves you from costly over-ordering or last-minute shortages. Steel is priced and sold by weight, so every calculation below converts a physical dimension into kilograms using the density of steel: 7,850 kg/m³.
1. Steel Plates
Formula: Weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.85
Example: a plate 2m long, 1m wide, 10mm thick → 2 × 1 × 10 × 7.85 = 157 kg.
2. Round Bars
Formula: Weight (kg/m) = Diameter (mm)² × 0.00617
Example: a 20mm diameter bar → 20² × 0.00617 = 2.47 kg/m. For a 6m bar, that's 14.8 kg.
3. Square Bars
Formula: Weight (kg/m) = Side (mm)² × 0.00785
Example: a 25mm square bar → 25² × 0.00785 = 4.9 kg/m.
4. Pipes (Hollow Round Sections)
Formula: Weight (kg/m) = (Outer Diameter − Wall Thickness) × Wall Thickness × 0.02466
Example: a pipe with 100mm OD and 5mm wall thickness → (100−5) × 5 × 0.02466 = 11.7 kg/m.
5. I-Beams and Channels
These use standardized weight-per-meter values published by steel manufacturers (e.g., ISMB, ISMC, or ASTM tables), since the cross-section isn't a simple rectangle. Always check the manufacturer's published kg/m rating rather than trying to calculate it from raw dimensions — the web-to-flange ratio varies by profile.
Common Mistakes to Avoid
- Forgetting to convert mm to meters consistently — mixing units is the single most common estimation error
- Using nominal (catalog) dimensions instead of actual measured dimensions for older or non-standard stock
- Ignoring cutting/wastage allowance — add 3–5% for real-world offcuts
- Assuming all steel grades have identical density — 7,850 kg/m³ is standard for mild steel/carbon steel; stainless steel is closer to 8,000 kg/m³
Skip the Manual Math
Our Steel Weight Calculator handles plates, bars, pipes, and beams instantly — just enter your dimensions and get an accurate weight in seconds, with support for multiple units.
Authored by Cold Matrix Engineering Team
Written and reviewed by our field engineering team at Cold Matrix Advanced Solutions — 10+ years of hands-on experience in cold storage, PU/PIR sandwich panels, PEB structures, and prefab construction across Pakistan and the Middle East.