# What is Unit Weight of Steel Bars ? : With Numerical Examples ( Specific Weight)

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**Steel is a variety of iron, containing 0.1 to 1.5% carbon in the form of cementite.** It is the most used element in civil engineering construction work. 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.**

It is also called the** specific weight of steel.**

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 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

( 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 rod of diameter 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 bar | 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 |