Calculate the exact weight of any steel section — round bars, flat plates, I-beams, channels, angles, and hollow sections — in seconds. Results in kg and tonnes with unit toggle.
Weight/m = d²/162 (d in mm)
Also use for MS sheet and chequered plate
Add wastage for offcuts during fabrication.
The fundamental formula is: Weight = Volume × Density. For steel the density is 7850 kg/m³. Volume equals cross-sectional area multiplied by length. For a 20mm round bar at 6m length: cross-sectional area = π/4 × 0.02² = 0.000314 m². Weight = 0.000314 × 6 × 7850 = 14.8 kg. The shortcut for round bar is d²/162 which gives kg per metre directly where d is diameter in mm. So 20²/162 = 2.47 kg/m × 6m = 14.8 kg.
The simplest and most commonly calculated section. Formula: kg/m = d²/162 where d is diameter in millimetres. This shortcut derives from π/4 × d² × 7850 / 1000000.
| Diameter (mm) | Weight (kg/m) | 6m Bar (kg) |
|---|---|---|
| 6 | 0.222 | 1.33 |
| 8 | 0.395 | 2.37 |
| 10 | 0.617 | 3.70 |
| 12 | 0.888 | 5.33 |
| 16 | 1.578 | 9.47 |
| 20 | 2.466 | 14.80 |
| 25 | 3.854 | 23.12 |
| 32 | 6.313 | 37.88 |
For flat sections: kg/m = Width(mm) × Thickness(mm) × 7.85 / 1000. Example: 100×10mm flat bar = 100 × 10 × 7.85 / 1000 = 7.85 kg/m. For plates use the same logic: kg = L(m) × W(m) × T(mm) × 7.85.
I-beams consist of two horizontal flanges connected by a vertical web. Cross-sectional area = 2 × (flange width × flange thickness) + web height × web thickness. Standard section tables (IS 808, BS 4) list theoretical weights per metre for each size. These are preferred over hand calculation because actual rolled sections have fillet radii at flange-web junctions that add material.
Hollow sections offer excellent structural efficiency with high strength-to-weight ratio. They are common in columns, purlins and trusses. For SHS: area = outer² – inner². For CHS: area = π/4 × (OD² – ID²). Wall thickness has a dramatic effect on weight — increasing wall from 3mm to 5mm on a 50mm SHS nearly doubles the weight.
Steel is sold by tonne or kg, not by piece count. Convert your piece requirement to total weight before requesting quotes. Add ±2.5% for mill rolling tolerance. When comparing supplier quotes, ensure you are comparing price per tonne (not per metre) since section sizes vary. Some suppliers quote running metre pricing for standard sections which can be converted using the kg/m value.
Both mild steel and structural steel have density of 7850 kg/m³ for weight calculation purposes. Steel grade affects yield strength (how much load it can carry) but not density. Common grades include IS 2062 (India), ASTM A36 (USA), S275 (Europe) and Grade 40/60 rebar in Pakistan. All use the same density for weight calculations.
Fabrication shops use this calculator to quote job weights for customer billing and material procurement. Structural engineers check preliminary member weights during design to estimate dead loads. Contractors calculate transport weights to select appropriate truck sizes and crane capacities for lifting. Site engineers verify delivery note quantities by cross-checking delivered weight against calculated weight. Students use it to verify steel design homework and learn weight formulas.
1. Using diameter instead of radius in the area formula (or vice versa). 2. Forgetting to multiply by quantity when ordering multiple pieces. 3. Using wrong density — 7800 instead of 7850, causing 0.6% error. 4. Mixing mm and metres in the same calculation without converting. 5. Not accounting for connections, gusset plates and weld metal which can add 3–5% to total structural weight.