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The Weight Formula for Steel

Weight Formula for Steel

If you’re in the metals industry, you know that there are a lot of factors to consider when it comes to calculating the weight of steel. Knowing the weight of steel is an important part of any project because it allows you to accurately estimate costs and plan accordingly. In this blog post, we’ll take a look at the various formulas for calculating the weight of steel.


The unit weight of any substance is defined as the mass or weight per unit volume ratio. It is commonly measured in pound/ft, gm/cm, kg/cm, or kg/m, for example.

The unit weight of materials varies depending on their composition and the properties of their constituent materials. It indicates the heaviness or lightness of the material.

The unit weight of steel

The weighted density of steel, or unit weight of steel, is the ratio of the weight of steel to its per unit volume. Steel weight calculator formula is typically expressed in kilograms per cubic meter (kg/m3). The unit weight of a mild steel plate or rolled steel is approximately 7850 kg/m3 or 7.85 g/cm3 or 78.5 KN/m3 or 489.84 lb/ft3. Steel weight is typically expressed in kilograms, tonnes, and pounds.

How to calculate weight of steel?

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

Example: Diameter of bar = 10mm and Length = 1 meter

Area of circular bar = p/4 × d

 = 3.14/4 × 102

= 78.5mm2

Volume = Area × Length

= 78.5 × 1000       (1 meter = 1000mm)

= 78500 mm3

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

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

Formula To Calculate the Weight of Steel Bars

The formula used to calculate the unit weight of steel bars is D²/162. Where, D = Dia. Of steel bars, 162 is a constant value.

Derivation of D2/162 Formula

Consider a steel bar with a diameter of D and a length is L.

Weight of Steel Bar (W) = Unit Weight of Steel Bar (γ)  x Volume (V)

W = γ x V

W =  πD²/4 x γ  (V = πD²/4)

As known that Steel unit weight is about 7850 kg/m3 (γ)

W =  πD²/4 x 7850

Here, D is steel diameter in mm, and the density of steel is in kg/m3. To make a constant value in the same unit we will convert Dia. Of steel in mm to m.

D² mm / 1000²

W =  π/4 x D²/1000² x 7850

W = D²/162.28 kg/m

W = D²/162 kg/m

Unit Weight Of Steel
Size Kg/m Kg/feet
6 mm 0.222 kg 0.067 kg
8 mm 0.395 kg 0.120kg
10 mm 0.617 kg 0.188 kg
12 mm 0.89 kg 0.270 kg
16 mm 1.58 kg 0.480 kg
20 mm 2.47 kg 0.751 kg
25 mm 3.86 kg 1.174 kg
32 mm 6.32 kg 1.925 kg

The Weight of Steel Plate and Sheets

The weight formula for sheet metal is fairly straightforward. The formula is as follows: Weight (lbs) = length (in) x width (in) x Thickness (in) x density (lb/in^3). For example, let’s say you have a piece of 1/4″ thick steel plate that measures 6″ x 8″. To calculate its weight, use this formula: 6″ x 8″ x 0.25″ x 10.2 lb/in^3 = 97.6 lbs.


The Weight of Steel Beams and Structures

Calculating the weight of steel beams and structures can be more complicated than calculating plate or sheet metal, since there are more variables to consider such as beam size, shape, orientation, etc. Generally speaking, most professionals use a method called “handbook calculation,” which takes into account all variables related to the structure’s design. This method is often used when designing bridges or other large-scale projects involving steel beams and structures.

The Weight of Steel Bars and Shapes

For calculating the weight of bars and shapes made from steel, use this formula: Weight (lbs) = length (ft) x width (ft) x thickness (ft) x density (lb/ft^3). For example, let’s say you have a piece of 4″ square bar stock that measures 8′ long. To calculate its weight using this formula, you would do the following math: 8′ x 4′ x 0.33′ ft^3 x 490 lb/ft^3 = 781 lbs.


The Weight of Steel Pipes

Many factors determine the weight of a steel pipe, including its length, diameter, and wall thickness. Although some basic calculations can be used to estimate the weight of a steel pipe, it is best to use the Weight formula for Steel pipes to obtain more accurate results. The Weight formula for Steel pipes states that: W = 0.02466 x D^2L / 10202, where “W” is the weight in kilograms per meter (kg/m), “D” is the outside diameter of the pipe in millimeters (mm), and “L” is its length in meters (m).



Calculating the exact mass of steel can be tricky depending on what type it is – plate or sheet metal, beams or structures, bars or shapes – but with these handy formulas, you should now have an easier time figuring out how much your materials weigh! Whether you’re working on small projects with sheets or large-scale projects with bars and shapes – understanding how to properly calculate steel weight can save time and money in your project planning process!


1. What is the unit weight of steel?

The unit weight or density of steel in kg/m3 is 7850kg/M3.

3. What is the formula for the weight calculation of steel bars?

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

4. What is the weight of the 12mm steel bar?

8mm = 0.396 kg/m

10mm = 0.619 kg/m

12mm = 0.888 kg/m

16mm = 1.58 kg/m

 5. What is the weight of the 8mm steel Plate?

The weight of an 8mm steel plate can vary depending on the dimensions and type of steel used. As a general estimate, an 8mm steel plate weighs approximately 62.8 kg/m² or 12.86 lb/ft².

6. Formula to Calculate Steel Quantity

The formula to calculate the quantity of steel required for a project depends on various factors such as the type of structure, design requirements, and engineering specifications. However, a commonly used formula to estimate the quantity of steel is:

Quantity of Steel = (Length of Steel Bar * Number of Bars * Weight of Steel per Unit Length)

2 thoughts on “The Weight Formula for Steel”

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