# How to calculate unit weight of steel bars?

## What is Steel?

Steel is the most versatile commonly used structural material. The essential elements in steel are metallic iron and non-metallic carbon, with small quantities of other elements such as silicon, nickel, manganese, chromium and copper.

It is thus an alloy. Though steel is usually more than 90% iron, with other elements present in small quantities, these other elements have a pronounced effect on the properties of steel.

### Unit Weight of Steel

Unit weight of steel or weight density of steel is the ratio of the weight of steel to its per unit volume. Usually, it is expressed in kilograms per cubic meter(kg/m3). The unit weight of steel is 7850 kg/m3 or 7.85 g/cm3 or 78.5 KN/m3 or 489.84 lb/ft3.

## Types of Steel

Depending upon the chemical composition, different types of steels are classified as:

1. Mild Steel
2. Medium Carbon Steel
3. High Carbon Steel.
4. Low Alloy Steel
5. High Alloy Steel

Out of these, the first three types of steel are known as structural steel, commonly used in steel structures.

In Indian standard IS:800-1984(Code of practice for general construction in steel) is applicable to the types of structural steels covered by the following Indian Standard:

1. IS:226-1975 Structural Steel (Standard Quality)

2. IS:1977-1975 Structural Steel (Ordinary Quality)

3. IS:2062-1984 Weldable Structural Steel

4. IS:961-1975  Structural Steel (High Tensile)

5. IS:8500-1977 Weldable Structural Steel (medium and high strength qualities)

Steel conforming to IS: 226-1975 is suitable for all types of structures subjected to static, dynamic and cyclic loading, and is suitable for welding up to 20 mm thickness. The physical properties of mild steel are as under:

1. Density or Unit Weight of Steel –  7850 kg/m3

2. Youngs’s modulus of elasticity (E)  –  2.04 x 105 Mpa (or N/mm2)

3. Modulus of Rigidity (G)                  –  0.785 x 105 Mpa (or N/mm2)

4. Poisson’s Ratio(µ)                             –  0.3 (inelastic rang)

5. Coefficient of thermal expansion or contraction  –   12 x 10-6 per °C or 6.7 x 10-6 per °F

## Calculation of Weight of steel bar for 1-metre Length

Weight = Density × Volume (Volume = Area x Length)

Example:-  Diameter of Bar = 10 mm and Length = 1 metre

Area of circular bar = π/4 × d2

= 3.14/4 × 102

=   78.5 mm

Volume      =   Area × Length

=    78.5 × 1000                  (1 metre = 1000 mm)

=    78500 mm3

Unit Weight of steel bar for 10 mm    =   (7850/1000 ×1000 ×1000) × 78500

=  0.616 kg/m               (1 kg/m3 = 0.000000001 kg/ mm3)

Similarly, we can calculate the unit weight of the square and rectangular bar.

Also, Read – How to Calculate Cutting Length of Stirrups for Beams and Columns

## Derivation of Formula forCalculating Unit Weight of Steel

As we know the density of steel  =  7850 kg/ m3

Weight of steel per metre     =  Volume × Density [ Volume = Area × Length ]

=  π/4 x d2 × 1000 × 7850 kg/m  (length = 1000 mm)

=  0.785 × d2 × 1000 × 7850 kg / (1000 × 1000  × 1000) [ 1 metre = 1000 mm ]

=  785 x d2 × 0.00000785

=    d2/1  ×  0.00616225 /1

=    d2/1/0.00616225

=    d2/162.27 ≈

=     d2/162   kg/m     (say)

Unit Weight of steel bar per feet    =  d2/(162.27 x 3.28084)         (  1 metre = 3.28084 feet)

=   d2/532.38 ≈

=   d2/533 (say)

=  d2/533  kg/feet

Also, Read What is Development Length? – Complete Guide

## FAQs

### What is the Unit weight of Steel?

Unit weight or weight density of steel = 7850 kg/m3

### How do you calculate the weight of steel?

Weight = Density × Volume (Volume = Area x Length)

Example:-  Diameter of Bar = 10 mm and Length = 1 metre
Area of circular bar = π/4 × d2
= 3.14/4 × 102
=   78.5 mm
Volume      =   Area × Length
=    78.5 × 1000                  (1 metre = 1000 mm)
=    78500 mm3
Unit Weight of steel bar for 10 mm    =   (7850/1000 ×1000 ×1000) × 78500
=  0.616 kg/m               (1 kg/m3 = 0.000000001 kg/ mm3)

### What is the formula for weight calculation of steel bars?

The formula for weight calculation of steel bars = d2/162   kg/m

### What is the weight of the 12 mm steel bar?

8 mm = 0.396  kg/m
10 mm = 0.619 kg/m
12 mm = 0.888 kg/m
16 mm = 1.58 kg/m

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### 8 thoughts on “How to calculate unit weight of steel bars?”

1. very good information sir

• 2. thank you sir

• You’re welcome.

3. Sir,
One small typo mistake I observed in this document for the table Unit Weight of Steel Bar Per Feet Length, in the table it is typed Weight of Bar Per Metre Length(D2/533)
This may make confusion. Plz correct the typo error

• Hi Santosh,
Thanks for reading the entire article and telling typing mistake. Now it has been updated.
Thanks!

4. • 