Complete Formula for Calculating Steel Weight

1、 The concept of theoretical weight of steel

The theoretical weight of steel is calculated based on its nominal size and density (formerly known as specific gravity), and is referred to as the theoretical weight. This is directly related to the length dimension, cross-sectional area, and allowable size deviation of the steel. Due to the allowable deviation of steel in the manufacturing process, the theoretical weight calculated by the formula may differ from the actual weight to some extent, so it is only used as a reference for estimation.

2、 Calculation formula for theoretical weight of steel

The unit of measurement for calculating the theoretical weight of steel is kilograms (kg). The basic formula is: W (weight kg)=F (cross-sectional area mm2) × L (length m) × ρ (density g/cm3) × 1/1000
The density of steel, ρ, is 7.85g/cm3, from which the theoretical weight calculation formulas for various types of steel are derived as follows:

Variety name: Threaded steel Calculation unit: kg/m Calculation formula: W=0.00617 × d2 Formula explanation: d=section diameter mm Calculation example: For a threaded steel with a section diameter of 12mm, calculate the weight per meter. Weight per meter=0.00617 × 122 ≈ 0.89kg

Variety name: Flat steel Calculation unit: kg/m Calculation formula: W=0.00785 × b × d Formula explanation: b=edge width, d=thickness mm Calculation example: For a flat steel with an edge width of 40mm and a thickness of 5mm, calculate the weight per meter. Weight per meter=0.00785 × 40 × 5=1.57kg

Variety name: Hexagonal steel
Calculation unit: kg/m Calculation formula: W=0.006798 × s2 Formula explanation: s=distance from the opposite side mm Calculation example: For a hexagonal steel with a distance of 50mm from the opposite side, calculate the weight per meter. Weight per meter=0.006798 × 502=16.995kg

Variety name: Octagonal steel
Calculation unit: kg/m Calculation formula: W=0.0065 × s2 Formula explanation: s=distance from the opposite side mm Calculation example: For octagonal steel with a distance of 80mm from the opposite side, calculate the weight per meter. Weight per meter=0.0065 × 802=41.6kg

Variety name: Equilateral angle steel
Calculation unit: kg/m Calculation formula: W=0.00785 × [d (2b – d)+0.215 (R2 – 2r2)] Formula explanation: b=edge width, d=edge thickness, R=inner arc radius, r=end arc radius (outer arc) Calculation example: Calculate the weight per meter of 20mm × 4mm equilateral angle steel. According to the metallurgical product catalog, the R value of 4mm × 20mm equilateral angle steel is 3.5, and the r value is 1.2. Therefore, the weight per meter is 0.00785 × [4 × (2 × 20-4)+0.215 × (3.52-2 × 1.22)]=1.15kg

Variety name: Unequal angle steel Calculation unit: kg/m Calculation formula: W=0.00785 × [d (B+b-d)+0.215 (R2-2r2)] Formula explanation: B=long side width, b=short side width, d=edge thickness, R=inner arc radius, r=end arc radius Calculation example: Calculate the weight per meter of 30mm × 20mm × 4mm unequal angle steel. According to the metallurgical product catalog, the R value of 30 × 20 × 4 unequal angle steel is 3.5, and the r value is 1.2. Therefore, the weight per meter is 0.00785 × [4 × (30+20-4)+0.215 × (3.52-2 × 1.22)]=1.46kg

Variety name: Channel steel Calculation unit: kg/m Calculation formula: W=0.00785 × [hd+2t (b-d)+0.349 (R2-r2)] Formula explanation: h=height, b=leg length, d=waist thickness, t=average leg thickness, R=inner arc radius, r=end arc radius Calculation example: Calculate the weight per meter of a channel steel of 80mm × 43mm × 5mm. According to the metallurgical product catalog, the channel steel t is 8, R is 8, and r is 4. Therefore, the weight per meter is 0.00785 × [80 × 5+2 × 8 × (43-5)+0.349 × (82-42)]=8.04kg

Variety name: I-beam
Calculation unit: kg/m Calculation formula: W=0.00785 × [hd+2t (b-d)+0.615 (R2-r2)] Formula explanation: h=height, b=leg length, d=waist thickness, t=average leg thickness, R=inner arc radius, r=end arc radius Calculation example: Calculate the weight per meter of 250mm × 118mm × 10mm I-beam. According to the metal material manual, the weight of the I-beam with t=13, R=10, and r=5 is 0.00785 × [250 × 10+2 × 13 × (118-10)+0.615 × (102-52)]=42.03kg per meter

Product Name: Steel Plate Calculation Unit: kg/m2 Calculation Formula: W=7.85 × d Formula Explanation: d=Thickness Calculation Example: For a steel plate with a thickness of 4mm, calculate the weight per m2. Weight per square meter=7.85 × 4=31.4kg

Variety name: Steel pipe (including seamless steel pipe and welding) Calculation unit: kg/m Calculation formula: W=0.02466 × S (D-S) Formula explanation: D=outer diameter, S=wall thickness Calculation example: For a seamless steel pipe with an outer diameter of 60mm and a wall thickness of 4mm, calculate the weight per meter. Weight per meter=0.02466 × 4 × (60-4)=5.52kg

3、 Other non-ferrous metals

Other non-ferrous metals include brass plate, brass plate, zinc plate, and lead plate. The weight calculation method is as follows:
Calculation method: specific gravity x thickness=weight per square meter (brass plate: specific gravity 8.5; purple copper plate: specific gravity 8.9; zinc plate: specific gravity 7.2; lead plate: specific gravity 11.37)

The formula for calculating the weight of brass tube is: (outer diameter wall thickness) x thickness x 0.0267 x length m
Example: Yellow copper tube 20mm x 1.5mm thick x 6m (length) Calculation: (20-1.5) x 1.5 x 0.0267 x 6=4.446kg

Formula for calculating the weight of copper tubes

Formula: (outer diameter wall thickness) x thickness x 0.02796 x length m
Example: Copper tube 20mm x 1.5mm thick x 6m (length) Calculation: (20-1.5) x 1.5 x 0.02796 x 6=4.655kg