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Steel weight calculator
Steel is priced by the ton but ordered by the piece, which is where most costing mistakes happen. Put in the section and the quantity, and this tells you what you are actually buying — in kilograms and in tons.
Sariya usually comes in 40 ft lengths.
Calculated at 7,850 kg/m³. Mill tolerance and coating shift the real figure slightly either way.
The formulas behind the numbers
Every one of these comes from the same idea: work out the cross-sectional area, multiply by length, multiply by the density of steel. Nothing more complicated than that.
| Section | Formula (kg per metre) | Worked example |
|---|---|---|
| Round bar | D² × 0.006165 | 16 mm → 1.578 kg/m |
| Square bar | A² × 0.00785 | 20 mm → 3.14 kg/m |
| Flat bar | W × T × 0.00785 | 50 × 6 → 2.36 kg/m |
| Hex bar | A/F² × 0.006798 | 24 mm A/F → 3.92 kg/m |
| Sheet / plate | W × T × 0.00785 | 1220 × 2 → 19.15 kg/m |
| Round pipe | (OD − T) × T × 0.02466 | 50 × 2 → 2.37 kg/m |
| Square tube | [A² − (A − 2T)²] × 0.00785 | 50 × 50 × 2 → 3.01 kg/m |
| Angle | T × (A + B − T) × 0.00785 | 50 × 50 × 5 → 3.73 kg/m |
Where 0.00785 comes from
Steel weighs 7,850 kg per cubic metre. Converted to work with millimetres and metres, that becomes the 0.00785 factor you see in every formula above.
Feet to metres
One foot is 0.3048 m, so a 40 ft bar is 12.192 m. Getting this conversion wrong is the single most common costing error we see.
Why the truck weighs more
Rolling tolerance, galvanised coating and mill practice all add a little. Plan with the calculated figure, invoice against the weighbridge.
About steel weights
About 0.888 kg per metre. A standard 40 ft bar is 12.192 m, so roughly 10.83 kg per bar — around 92 bars to the ton. For 16 mm it is 1.578 kg/m and about 52 bars to the ton.
Multiply length in metres by width in metres by thickness in millimetres by 7.85. A 8×4 ft sheet at 1 mm comes out around 23.4 kg. Galvanised coating adds a small amount on top, depending on whether it is Z80 or Z275.
Yes, with one adjustment. The zinc coating adds weight — roughly 1 to 3 per cent depending on whether it is Z80 or Z275. Work out the base steel weight here, then add the coating allowance, or send us the spec and we will confirm the delivered weight.
Yes, for estimating. It is the same arithmetic a quantity surveyor uses. For the final invoice the weighbridge figure governs, and any reasonable supplier will show you it.
Steel is sold by weight, not by piece
Three places a wrong weight costs money, and how to avoid each one.
Budgeting a job
A drawing gives you lengths and sections. The rate is per ton. Convert before you price the job, not after, or the margin disappears between the two.
Checking a delivery
Work out what the load should weigh before it arrives. If the bridge figure and your figure disagree by more than mill tolerance, ask before you unload.
Planning transport
A single 100 mm round bar at 40 ft is over 300 kg. Knowing the tonnage decides whether it is a pickup, a truck or a trailer.
Got your tonnage? Now get the rate.
Send the specification straight from the calculator, or message us the whole size list at once.