Calculator
Bright bar weight calculator
Steel is priced by weight and specified by dimension. Convert between the two for round, hex and square bar — then send us the requirement in one click.
Bright Bar Weight Calculator
Nominal diameter of the bar
Based on a steel density of 7,850 kg/m³ and the nominal dimension. Actual weighed quantity varies slightly because a cold drawn bar to an h-tolerance is never above nominal size. Use this for estimating and ordering; invoicing is on weighbridge weight.
Result
- Weight per metre
- 2.4662 kg
- Weight per piece
- 7.398 kg
- Total weight
- 739.85 kg
- Total length
- 300 m
0.7398 MT
The formulas
Where the constants come from
Weight per metre is cross-sectional area multiplied by density. Working in millimetres and metres with a steel density of 7,850 kg/m³, every formula reduces to dimension squared times a constant.
Full article, with a worked example| Shape | Cross-sectional area | Weight per metre (kg) |
|---|---|---|
| Round | π/4 × d² | d² × 0.0061654 |
| Hex | (√3/2) × AF² | AF² × 0.0067983 |
| Square | a² | a² × 0.0078500 |
d = diameter, AF = across flats, a = side. All in millimetres.
Questions
Frequently asked
Four things worth knowing before you rely on a calculated figure.
- How do you calculate the weight of a round steel bar?
- Weight per metre = d² × 0.006165 kg, where d is the diameter in millimetres. The constant comes from the cross-sectional area (π/4 × d²) multiplied by a steel density of 7,850 kg/m³.
- How do you calculate the weight of a hex bar?
- Weight per metre = AF² × 0.006798 kg, where AF is the across-flats dimension in millimetres. The constant comes from the hexagonal area (√3/2 × AF²) times 7,850 kg/m³. Hex bar is roughly 10% heavier than round at the same nominal size.
- Why does the calculated weight not match the weighbridge?
- The formula uses the nominal dimension. A cold drawn bar to an h-tolerance is never above nominal and is usually slightly under it, so actual weight is typically a little below calculated. Cut length tolerance and small density variation between grades also contribute. Use the calculation for estimating and ordering; invoicing is on weighbridge weight.
- Is hex bar measured across flats or across corners?
- Always across flats. The across-corners dimension is about 15.5% larger, and using it in the formula will substantially overstate the weight — one of the most common ordering errors.
Tell us what you need
Worked out the tonnage? Send us the grade, shape, size and quantity and we will confirm availability and price.