Metal Weight Calculator
Pick a shape and material, enter dimensions, get the weight in kg and lb — with nominal densities and mill-tolerance guidance.
Last updated: 2026-09-15
How the calculation works
- Volume comes from the standard geometry for each shape; weight is volume × nominal density.
- Densities are typical alloy values at room temperature (steel 7.85 g/cm³, aluminum 2.70, etc.).
Formula
Weight = Volume × density Round: V = π/4 × d² × L ... Tube: V = π/4 × (OD² − ID²) × L
| Symbol | Meaning | Unit |
|---|---|---|
ρ | Material density | g/cm³ |
V | Volume of the shape | cm³ |
Worked example
A 20 mm × 1 m round steel bar: V = π/4 × 4 cm² × 100 cm = 314 cm³ → 2.47 kg (5.44 lb). A 48 × 3 mm tube of the same length: 1.06 m of stock weighs 3.36 kg — tubes trade weight for stiffness efficiently.
Interpreting the result
Weight drives shipping, structural load and material cost. Order 2% extra for mill tolerance and offcuts. The kg/m figures are also how steel is priced — knowing a 20 mm bar is 2.47 kg/m lets you sanity-check quotes instantly.
Assumptions
- Nominal densities; specific alloys vary ±1–2%.
- Prism shapes with uniform cross-section.
Limitations
- Exotic alloys, castings with draft, and machined parts need measured volumes.
- Temperature expansion affects weight only trivially.
Frequently asked questions
How much does a steel plate weigh per m²?
Multiply thickness in mm by 7.85: a 6 mm plate is 47.1 kg/m². The rule: kg/m² = 7.85 × t(mm).
Why is aluminum so much lighter?
Density 2.70 vs steel's 7.85 — about a third. But aluminum's stiffness is also a third, so equal-stiffness parts save less weight than density suggests.