Steel Weight Calculation Formula — D²/162 Explained with Complete Table
Every civil engineer and contractor needs to calculate the weight of steel bars for estimation, billing, and procurement. The universal formula used across India is D²/162. Here's everything you need to know.
The Formula
Where D = diameter of the bar in mm.
Why 162?
The full derivation: Weight = Cross-sectional area × Length × Density
= (π/4) × D² × 1m × 7850 kg/m³
= (3.14159/4) × (D/1000)² × 7850
= D² / 162.28 ≈ D² / 162
Complete Steel Weight Table
| Diameter (mm) | Weight/Meter (kg) | Weight/Rod 12m (kg) | Rods per Tonne | Price/Rod (₹)* |
|---|---|---|---|---|
| 6 | 0.222 | 2.67 | 375 | ₹187 |
| 8 | 0.395 | 4.74 | 211 | ₹332 |
| 10 | 0.617 | 7.40 | 135 | ₹518 |
| 12 | 0.888 | 10.66 | 94 | ₹746 |
| 16 | 1.580 | 18.96 | 53 | ₹1,327 |
| 20 | 2.469 | 29.63 | 34 | ₹2,074 |
| 25 | 3.858 | 46.30 | 22 | ₹3,241 |
| 32 | 6.321 | 75.85 | 13 | ₹5,310 |
* Approximate price at ₹70/kg (2026 average). Actual prices vary by brand and location.
Quick Examples
Example 1: Weight of 10 nos 12mm bars, each 6m long:
Example 2: Weight of 16mm bar, 4.5m long:
Steel Required for Common Structures
| Structure | Steel (kg/m³ concrete) | Typical Bars |
|---|---|---|
| Residential Slab | 80 – 100 kg/m³ | 8mm, 10mm, 12mm |
| Column | 150 – 200 kg/m³ | 12mm, 16mm, 20mm |
| Beam | 120 – 160 kg/m³ | 12mm, 16mm, 20mm |
| Foundation | 60 – 90 kg/m³ | 10mm, 12mm, 16mm |
| Staircase | 100 – 130 kg/m³ | 10mm, 12mm |
Instant Steel Weight Calculator
Enter diameter, length, and quantity — get weight + cost instantly.
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What is the formula to calculate steel weight?
Weight (kg/m) = D² / 162, where D is diameter in mm. Example: 12mm bar = 12²/162 = 0.888 kg/m.
How much does a 12mm steel bar weigh?
A 12mm TMT bar weighs 0.888 kg per meter. A standard 12m rod weighs 10.66 kg.
How many 12mm rods in 1 tonne?
Approximately 94 rods of 12mm (12m length) make 1 tonne (1000 kg).
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