How do you calculate the weight of steel?
Steel weight comes from volume × density. Work out the cross-sectional area of the profile, multiply by the length to get the volume, then multiply by the density of steel — about 7,850 kg/m³ (7.85 g/cm³, or roughly 490 lb/ft³). The hard part is the area of odd profiles like I-beams and angles, which is why the calculator holds the formula for each shape so you just enter the dimensions.
Weight of round bar and rebar
For a solid round bar, a handy shortcut is weight (kg/m) = d² ÷ 162, where d is the diameter in millimetres. So a 12 mm bar is 144/162 ≈ 0.89 kg per metre, a 16 mm bar about 1.58 kg/m, and a 20 mm bar 2.47 kg/m. This d²/162 rule is used on site all over the world for reinforcing steel; the calculator applies it (and the equivalents for other shapes) automatically.
Plate, sheet and flat bar
Steel plate is the easy one: area × thickness × density. A shortcut in metric is that a plate weighs about 7.85 kg per square metre for every millimetre of thickness, so a 10 mm plate is ~78.5 kg/m². Multiply by your sheet's length and width for the total. This is the number you need for lifting plans and for checking whether a rack, trailer or floor can take the load.
Why steel weight matters before you order
Steel is priced and freighted by weight, and cut to length, so knowing the weight up front tells you the cost, the delivery, and whether you can lift or move it safely. It also feeds structural checks — a beam's self-weight is part of the load it has to carry. Getting the profile and dimensions right in the calculator gives you a figure you can put straight into a quote or a lifting plan.
Uses a standard carbon-steel density (7,850 kg/m³). Stainless, alloy and cast steels differ; confirm the exact grade for critical work.
Frequently asked questions
How do I calculate steel weight?
Cross-sectional area × length × steel density (7,850 kg/m³). The calculator holds the area formula for each profile so you just enter the dimensions.
What is the weight of a 12mm steel bar?
About 0.89 kg per metre, using the rule weight (kg/m) = d²/162 for round bar (12²/162 = 0.888).
How much does steel plate weigh?
About 7.85 kg per square metre per millimetre of thickness — so a 10 mm plate is ~78.5 kg/m². Multiply by length × width.
What is the density of steel?
About 7,850 kg per cubic metre (7.85 g/cm³, ~490 lb/ft³). Stainless and alloy steels vary slightly.
What is the d²/162 rule?
A quick way to get round-bar weight in kg/m: square the diameter in mm and divide by 162. A 16 mm bar is 256/162 ≈ 1.58 kg/m.