Squares and rectangles (rectangular) cross-section of carbon steel pipe:
      Weight per meter unit: kg / m (kg / m) & lb / ft (lb / ft)
Rectangular pipe commonly used to facilitate a calculation formula:
                  (Length width) × 2 ÷ 3.14-thickness × thickness × 0.02466 = kg / m
                 Formula II:
                     kg / m = (Oc - 4Wt) * Wt * 0.00785
                     Oc is the pipe outside the perimeter, Wt is the pipe wall thickness;
                     Oc = 4 * a square
                     Rectangular Oc = 2a 2b a, b is the side length
Popular explanation is: 4x thickness x (side - wall thickness) x7.85
Among them, the square tube side and wall thickness are in millimeters directly to the values ​​into the above formula, obtained is the weight per meter square tube, in grams.
If 30x30x2.5 mm square tube, according to the formula to calculate the weight per meter:
4x2.5x (30-2.5) x7.85 = 275x7.85 = 2158.75 grams, or about 2.16 kg
When the wall thickness and the side units are in mm, 4x thickness x (side - wall thickness) is calculated per meter length of the square tube volume, in cubic centimeters as a unit, multiplied by the proportion of iron per cubic centimeter 7.85 grams obtained per meter square tube is the unit weight in grams.