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Metal Bar Weight Calculation
Guide · Updated October 28, 2026
Knowing what a piece of stock weighs helps you quote material, size a lifting method, check a shipment, and confirm the metal type. Weight is just volume times density. The only work is getting the cross-section area right for the shape.
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Step by step
- Measure the stock: Diameter or across-flats, thickness, width, wall and length, all in inches (or all in mm).
- Find the area: Round: 0.7854 × D². Hex: 0.866 × AF². Square: AF². Plate: T × W. Tube: 0.7854 × (OD² − ID²).
- Find volume: Volume = area × length.
- Multiply by density: Weight = volume × density in lb/in³.
- Check against a chart: Compare lb per foot with a supplier weight chart to catch decimal errors.
Densities
Typical values in lb/in³: carbon steel 0.2836, 304 stainless about 0.289, 6061 aluminum about 0.0975, 7075 aluminum about 0.101, C360 brass about 0.307, C110 copper about 0.323, titanium 6Al-4V about 0.160 and gray cast iron about 0.26. Metric: steel 7.85 g/cm³, 6061 aluminum 2.70 g/cm³, brass about 8.5 g/cm³.
Worked example: steel round
A 2.000 in diameter steel bar, 12 in long: area = 0.7854 × 4 = 3.1416 in², volume = 37.70 in³, weight = 37.70 × 0.2836 = 10.69 lb. Supplier charts list 2 in round steel at about 10.68 lb/ft, so the math checks.
The same bar in 6061 aluminum weighs 37.70 × 0.0975 = 3.68 lb, a little over a third of the steel.
Worked example: hex and plate
A 1.000 in across-flats steel hex, 36 in long: area = 0.866 × 1 = 0.866 in², volume = 31.18 in³, weight = 8.84 lb (2.95 lb/ft).
A 1/2 × 6 × 24 in 6061 plate: volume = 0.5 × 6 × 24 = 72 in³, weight = 72 × 0.0975 = 7.02 lb.
Worked example: tube
Steel tube 2.000 in OD × 0.250 in wall (ID 1.500 in), 48 in long: area = 0.7854 × (4.000 − 2.250) = 1.374 in², volume = 65.97 in³, weight = 18.7 lb. A common mistake is to subtract diameters before squaring; (2.000 − 1.500)² would give an area that is far too small.
Metric example
A 50 mm diameter steel bar, 1 m long: area = 0.7854 × 50² = 1963 mm², volume = 1,963,000 mm³ = 1963 cm³, weight = 1963 × 7.85 = 15.4 kg.
Common problems
Mixing inches and feet in length, using aluminum density for steel, measuring hex across corners instead of flats, and forgetting the kerf and facing stock when quoting cut blanks.
FAQ
What is the density of steel?
About 0.2836 lb/in³ or 7.85 g/cm³.
How do I find weight per foot?
Area in in² × 12 × density.
Why measure across flats on hex?
The 0.866 × AF² area formula uses across-flats.
How do I check my caliper before measuring stock?
Check it against gage blocks; build any stack free at gageblockcalc.com.
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