📐Derivation of Steel Bar Weight Formula (D²/162)

💫The formula D²/162 is a quick method used by civil engineers to calculate the weight of a steel reinforcement bar (rebar) per meter.

🚧Step-by-Step Derivation:

1. Area of Steel Bar

Steel bars have a circular cross-section.

Area = πD²/4

2. Volume of 1 Meter Steel Bar

Volume = Area × Length

Since 1 m = 1000 mm:

Volume = (πD²/4) × 1000 mm

3. Density of Steel

Standard density = 7850 kg/m³

4. Weight Calculation

Weight = Volume × Density

After simplifying and converting units:

Weight of 1 meter steel bar = D²/162 kg/m

🏷Example:

8 mm bar: 8²/162 = 0.395 kg/m

10 mm bar: 10²/162 = 0.617 kg/m

12 mm bar: 12²/162 = 0.889 kg/m

16 mm bar: 16²/162 = 1.58 kg/m

20 mm bar: 20²/162 = 2.47 kg/m

25 mm bar: 25²/162 = 3.86 kg/m

💡 Remember: This formula is widely used for estimating reinforcement steel quantities quickly during design, estimation, and site execution.

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