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**Steel is a variety of iron, containing 0.1 to 1.5% carbon in the form of cementite.** It is a widely used civil engineering construction material with high tensile strength. After knowing the unit weight of steel, we can determine the total weight of steel bars required for the project construction.

** 1. Unit Weight of Steel Bars – In kg/m³ **

**It is the ratio of the weight of steel per unit volume.**

Its SI unit is **kg/m³**.

Unit weight of steel is **7850 kg/m³.**

** 2. Unit Weight of Steel Bars – In Kg/m **

**It is the ratio of the weight of steel per unit length**.

It is expressed in** kg/m**.

** a. Determination of unit weight of flat steel bars **

For determining the unit weight of flat steel bars; the thickness and width of the flat bar should be known.

Take steel density as 7850 kg/m³ and the length of the bar as unity.

The formula for calculating the weight of the flat bar,

Weight = Volume × Density

Weight of flat steel bar= (Length × Width × Thickness) × Density of steel

**Unit weight of flat steel bar = ( 1 × Width × Thickness) × Density of steel**

**Numerical**

**Determine the unit weight of flat steel of thickness 10 mm and width 20 mm.**

Solution,

Weight of flat steel = Volume of steel × Density of steel

Weight of flat steel = (Length × Width × Thickness) × Density of steel

Unit weight of flat steel = ( 1 × 0.02 × 0.01) × 7850

= 1.57 kg/m

** b. Determination of unit weight of circular steel bars **

This function is only applicable for circular steel bars whose density is 7850 kg/m³.

Consider,

The length of the rod is unity ( 1m ).

The density of steel is 7850 kg/m³.

Take **d** as the diameter of the rod (in mm).

**The weight of the steel rod is calculated as:**

Weight of steel rod = Volume of steel rod × Density of steel

Weight of steel rod = (Cross-sectional Area of rod × Length) × Density of steel

Unit weight of steel rod = ( πd²/4 × 1) × 7850

= ( πd²/4 × 1000) × 7850/1000000

= d²/162 kg/m

{ 1m length= 1000 mm length

7850 kg/m³ = 7850/ (100 *100*100) = 7850/1000000 kg/mm³}

**Unit weight of steel rod = d²/162 **kg/m

where,

d= diameter of steel rod in mm

Again,

**Unit weight of steel rod = d²/533 **kg/foot

where,

d= diameter of rod in mm

**Numerical**

**Determine the unit weight of steel rods of diameters 10 mm and 20 mm.**

Solution,

Unit weight of steel rod for** 10 mm** diameter **= d²/162 = 10² / 162**

**= 0.617 kg/m**

Unit weight of steel rod for **20 mm** diameter** = 20² / 162**

**= 2.469 kg/m**

**Unit Weight of Circular Bars – In meter**

Diameter of bar |
Weight of 1 m length |

6 mm | 0.22 kg |

8 mm | 0.39 kg |

10 mm | 0.62 kg |

12 mm | 0.88 kg |

16 mm | 1.58 kg |

20 mm | 2.47 kg |

25 mm | 1.388 kg |

28 mm | 4.839 kg |

**Unit Weight of Circular Bars – In Feet**

Diameter of the bar (mm) |
Weight of 1 feet length |

8 | 0.120 |

10 | 0.187 |

12 | 0.27 |

16 | 0.48 |

20 | 0.75 |

25 | 0.422 |

28 | 1.471 |

32 | 1.921 |

40 | 3.00 |

Read More: Lap Length |

Read More: Preliminary Estimate |