Plate Weight Formula
Plate weight is density times width, thickness and length. For steel plate, 1 mm thickness weighs 7.85 kg per square metre, so kg/m² = 7.85 × thickness in mm.
Open the metal weight calculatorPlate and sheet formula
A plate is a rectangular prism, so the cross-section area is A = width × thickness
and the weight is:
W = ρ · w · t · L
With dimensions in mm and density in g/cm³,
weight (kg) = ρ · w · t · L / 1,000,000.
For area-based estimating, steel plate weighs 7.85 × t kg/m² with
t in mm. A 10 mm steel plate is therefore 78.5 kg/m²
before coating, scale or cutouts.
Worked example
A 250 mm wide, 10 mm thick mild-steel plate strip that is 1 m long has volume
250 × 10 × 1000 = 2,500,000 mm³. Weight is
7.85 × 2,500,000 / 1,000,000 = 19.6 kg.
Sheet, flat bar and plate use the same math
The name changes with thickness and stock form, but the weight formula does not. Sheet, strip, flat bar and rectangular plate all use width times thickness times length. For blanks with holes, slots or a profile cut from the edge, subtract the removed area times thickness before multiplying by density.
Material changes
Aluminum plate is about a third of steel by weight: 6061 aluminum at 2.70 g/cm³ makes a 10 mm plate roughly 27.0 kg/m². 304 or 316 stainless at about 8.00 g/cm³ makes the same 10 mm plate roughly 80.0 kg/m². Use the calculator when the material is not mild steel.
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Last reviewed: June 1, 2026.