Steel weight formulas.

Density: A practical value of 7.85 g/cm³ is used for carbon and alloy steels. Results are theoretical; actual scale weight may vary with production tolerance.

Round steel bar

Kg = π / 4 × diameter² × length × quantity × 7.85 / 1,000,000

Example: Ø75 × 3000 mm, 1 piece ≈ 104.04 kg.

Square steel

Kg = side × side × length × quantity × 7.85 / 1,000,000

Flat / rectangular steel

Kg = width × thickness × length × quantity × 7.85 / 1,000,000

Hexagonal steel

Kg = 0.866025 × across-flats² × length × quantity × 7.85 / 1,000,000

Steel tube

Kg = π / 4 × (outer diameter² − inner diameter²) × length × quantity × 7.85 / 1,000,000

Unit check: area (mm²) × length (mm) × density (kg/m³) × 10⁻⁹ gives kilograms per piece. 7.85 g/cm³ equals 7850 kg/m³. Hexagon size means across flats, not across corners. For tubes, inner diameter = outer diameter − 2 × wall thickness; wall thickness must be positive and less than half the outer diameter. These are theoretical estimates, not scale weight or a binding quotation.

Cut-size note

The calculator uses the dimensions entered, without hidden diameter, thickness, length or saw allowances. Enter the intended material dimensions. Saw kerf concerns cutting-plan length consumption; machining allowances require a separately confirmed drawing and order specification.

Rounding method

First calculate the unrounded piece weight multiplied by the row quantity. Round that row total up to a whole kilogram only once. The rounded grand total is the sum of these rounded row totals; it is separate from the net theoretical total. Do not round each piece before multiplying by quantity.