Engineering Tools

Mechanical design calculator

Material Weight Calculator

Estimate the mass of plates, solid bars, hollow tubes and angle profiles using standard material densities or a custom value.

Rectangular Plate / Flat Bar cross-section Simplified cross-section of the selected material profile. width t
Selected profile: Rectangular Plate / Flat Bar Simplified cross-section; not to scale.

Profile dimensions

Cross-section dimensions are entered in millimetres.

How material weight is calculated

The calculator first finds the cross-sectional area of the selected profile, multiplies it by length to obtain volume, and then multiplies the volume by material density.

General formula

m = ρ × A × L

  • m = material mass
  • ρ = material density
  • A = cross-sectional area
  • L = profile length

In purchasing and fabrication, “weight” is commonly reported in kilograms or pounds. Strictly speaking, these are units of mass; force weight would be expressed in newtons or pound-force.

Supported profile formulas

Profile Cross-sectional area
Plate / flat barA = width × thickness
Round barA = πd² / 4
Square barA = width²
Round tubeA = π(D² − d²) / 4
Square tubeA = B² − (B − 2t)²
Rectangular tubeA = BH − (B − 2t)(H − 2t)
Angle profileA = t(a + b − t)

Nominal material densities

Built-in densities are representative values suitable for estimating. Actual density can vary with alloy, grade, composition, porosity and temperature.

Material Density
Carbon steel7,850 kg/m³
Stainless steel8,000 kg/m³
Aluminum2,700 kg/m³
Copper8,960 kg/m³
Brass8,500 kg/m³
Cast iron7,200 kg/m³

Worked example: steel flat bar

Find the mass of a carbon-steel flat bar that is 100 mm wide, 10 mm thick and 2 m long.

  1. Area: 100 × 10 = 1,000 mm² = 0.001 m².
  2. Volume: 0.001 × 2 = 0.002 m³.
  3. Mass: 7,850 × 0.002 = 15.7 kg.

Result: 15.7 kg per piece

Common uses

  • Estimating raw-material orders and transport loads.
  • Comparing alternative materials and section sizes.
  • Preparing fabrication quotations and cutting lists.
  • Estimating component mass during early-stage design.
  • Checking workshop and warehouse inventory.

Common mistakes

  • Mixing millimetres, metres, inches and feet.
  • Using outer tube dimensions as though the section were solid.
  • Applying a generic density to an alloy requiring tighter accuracy.
  • Forgetting to multiply the single-piece result by quantity.
  • Ignoring holes, chamfers, coatings or manufacturing tolerances.

Frequently asked questions

Is the calculated value mass or weight?

The calculator returns mass in kilograms and pounds, following common material-supply terminology. To find force weight, multiply mass by gravitational acceleration.

Are the built-in densities exact?

No. They are nominal representative values. Use the custom-density option when a material certificate, specification or manufacturer provides a more suitable value.

Does the tube calculation include rounded corners?

No. Square and rectangular tubes are treated as ideal sharp-cornered sections. Published section mass from the manufacturer is preferable when production geometry matters.

Does the angle calculation include root radii?

No. The angle profile uses an idealized sharp-corner formula. Rolled angles can differ because of root radii and manufacturing tolerances.

Can I enter a density in imperial units?

Yes. When Imperial is selected, custom density is entered in pounds per cubic foot. Metric custom density is entered in kilograms per cubic metre.

Accuracy and responsible use

Results are estimates based on ideal geometry and the density selected by the user. Verify consequential purchasing, lifting, structural and manufacturing decisions against drawings, standards, certificates and supplier data.

Read the Methodology & Accuracy page and the Terms & Disclaimer .