Steel is a widely used construction material with 0.1-1.5% **carbon in cementite**. This article discusses the unit weight of steel bars.

**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**.

The 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 also expressed in** kg/m**.

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

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

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 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 only applies to circular steel bars with a density of 7850 kg/m³.

**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 foot 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 |

**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 10 mm and 20 mm diameters.**

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**

Read More: Lap Length |

Read More: Preliminary Estimate |