- Weight = volume × density; SS 304 density is 7.93 g/cm³, SS 316 about 7.98 and 400-series about 7.7.
- Sheet/plate: kg = length (m) × width (m) × thickness (mm) × 7.93.
- Pipe: kg/m = (OD − WT) × WT × 0.02491 (OD and WT in mm).
- Round bar: kg/m = diameter² (mm) × 0.00623.
Stainless steel is priced per kilogram, so the first step in any quote is to work out the weight. These formulas use millimetres and give kilograms, with the density of SS 304 (7.93 g/cm³). For 316 multiply by 1.006; for 400-series grades multiply by 0.977.
Sheet and plate
Weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.93
Example: a 1250 × 2500 mm sheet, 2 mm thick → 1.25 × 2.5 × 2 × 7.93 = 49.6 kg.
Round bar
Weight per metre (kg) = Diameter² (mm) × 0.00623
Example: a 40 mm bar → 40 × 40 × 0.00623 = 9.97 kg/m.
Pipe and round tube
Weight per metre (kg) = (OD − WT) × WT × 0.02491
Example: 3" Sch 10S pipe, 88.90 mm OD × 3.05 mm → (88.90 − 3.05) × 3.05 × 0.02491 = 6.52 kg/m.
Square tube
Weight per metre (kg) = 4 × WT × (Side − WT) × 0.00793
Example: 50 × 50 × 2 mm → 4 × 2 × 48 × 0.00793 = 3.05 kg/m.
Rectangular tube
Weight per metre (kg) = 2 × WT × (A + B − 2 × WT) × 0.00793
Flat bar
Weight per metre (kg) = Width × Thickness × 0.00793
Equal angle
Weight per metre (kg) = (2 × Leg − Thickness) × Thickness × 0.00793
Hexagonal and square bar
Hex bar (across flats A): A² × 0.00687 kg/m. Square bar: A² × 0.00793 kg/m.
Don't want to do the maths? Use our free stainless steel weight calculator — choose the shape, grade and size, and it also estimates the cost at your rate.