How to convert metres and m² into tonnes
To convert metres of pipe or m² of sheet into tonnes, you need the mass of one metre or of one square metre. Stainless steel has a density of 7.9 g/cm³, so the weight of 1 m² of sheet 1 mm thick is 7.9 kg, and a metre of 57×3 pipe weighs 4.02 kg.
Then the length in metres is multiplied by the mass of a linear metre, the area by the mass of a square metre, and the result is divided by 1000.
Below — why this conversion arises at all, formulas for sheet and pipe, ready-made tables and a calculation procedure without a calculator.
Why the price is per tonne, but buying is by the metre
The tonne is a single measure for any product range. Sheet, pipe, round bar and angle are compared directly in tonnes, but not in metres and squares: a metre of 16×1 pipe and a metre of 108×4 pipe differ in weight by a factor of twenty.
Hence two practical tasks. The first is to understand how many tonnes you are ordering if the volume is calculated in metres or sheets. The second is to understand how many metres will arrive in a tonne, in order to verify the shipment.
In an order on the exchange, the unit of quantity is specified, and it is fixed together with the commodity. If you are used to counting in metres, convert the volume in advance: then supply and demand will meet in one unit and the matching will proceed without renegotiation.
Conversion for sheet: the weight of 1 m² of stainless steel
The mass of a square metre is equal to the thickness in millimetres multiplied by the density:
m (kg/m²) = t × 7.9
| Thickness, mm | Weight of 1 m², kg | Sheet 1250×2500, kg | Sheet 1500×3000, kg |
|---|---|---|---|
| 0.8 | 6.32 | 19.75 | 28.44 |
| 1.0 | 7.90 | 24.69 | 35.55 |
| 1.2 | 9.48 | 29.63 | 42.66 |
| 1.5 | 11.85 | 37.03 | 53.33 |
| 2.0 | 15.80 | 49.38 | 71.10 |
| 2.5 | 19.75 | 61.72 | 88.88 |
| 3.0 | 23.70 | 74.06 | 106.65 |
| 4.0 | 31.60 | 98.75 | 142.20 |
| 5.0 | 39.50 | 123.44 | 177.75 |
| 6.0 | 47.40 | 148.13 | 213.30 |
| 8.0 | 63.20 | 197.50 | 284.40 |
| 10.0 | 79.00 | 246.88 | 355.50 |
Reverse conversion: a tonne contains as many square metres as the mass of 1 m² fits into 1000 kg. For 2 mm sheet this is 1000 / 15.8 = 63 m². For 6 mm sheet — 21 m².
The area of a sheet is calculated simply: 1250 × 2500 mm is 3.125 m², 1500 × 3000 mm is 4.5 m².
Conversion for pipe
For a round pipe, the mass of a metre is calculated from the wall and the diameter:
m = 0.0248 × S × (D − S)
where S is the wall thickness, D is the outside diameter, both in millimetres. The coefficient 0.0248 is derived from the density of 7.9 g/cm³.
| Size, mm | Weight of 1 m, kg | Metres per tonne |
|---|---|---|
| 16×1 | 0.37 | 2686 |
| 20×1.5 | 0.69 | 1452 |
| 25×1.5 | 0.88 | 1143 |
| 32×2 | 1.49 | 672 |
| 38×2 | 1.79 | 560 |
| 45×2 | 2.13 | 468 |
| 57×3 | 4.02 | 249 |
| 76×3 | 5.44 | 184 |
| 89×3 | 6.40 | 156 |
| 108×3 | 7.82 | 128 |
| 108×4 | 10.33 | 97 |
Example: 300 metres of 57×3 pipe are needed. The mass of a metre is 4.02 kg, so the volume equals 300 × 4.02 = 1206 kg, that is, 1.21 tonnes. Conversely: a tonne of such pipe contains 249 metres.
For profile pipe the formula is more complex, because the cross-section is not round. The practical way is to take the mass of a metre from the manufacturer's tables or to calculate the perimeter of the cross-section with the corner radii. The error on the radii is small, but over a tonne a noticeable difference accumulates.
Calculator
The calculation procedure without special software:
- Determine the density. For stainless steel take 7.9 g/cm³ — this is sufficient for an order and for verification.
- Calculate the mass of a unit: for sheet, thickness × 7.9; for round pipe, 0.0248 × S × (D − S); for round bar, 0.0062 × d².
- Multiply by the quantity: metres, square metres or the number of sheets.
- Divide by 1000 — you get tonnes.
| What we convert | Formula for the mass of a unit | Unit |
|---|---|---|
| Sheet | t × 7.9 | kg per 1 m² |
| Round pipe | 0.0248 × S × (D − S) | kg per 1 m |
| Round bar | 0.0062 × d² | kg per 1 m |
The calculation gives a theoretical weight. It relies on nominal dimensions, while rolled steel is produced with tolerances, so the actual mass of a batch may differ. For acceptance, rely on the certificate and weighing, and use the formula for planning.
Frequently asked questions
How much does 1 m² of 1 mm stainless steel weigh?
7.9 kg at a density of 7.9 g/cm³. The mass grows linearly: 2 mm — 15.8 kg, 3 mm — 23.7 kg, 10 mm — 79 kg per square metre.
How to convert metres of pipe into tonnes?
Multiply the length in metres by the mass of one metre and divide by 1000. Take the mass of a metre from the table or calculate it using the formula 0.0248 × S × (D − S). For example, 300 metres of 57×3 pipe is 1.21 tonnes.
How to convert m² of sheet into tonnes?
Multiply the area by the mass of a square metre at the required thickness and divide by 1000. 40 m² of 3 mm sheet is 40 × 23.7 = 948 kg, that is, 0.95 tonnes.
How many m² of sheet are in a tonne?
It depends on the thickness: the thicker the sheet, the fewer squares in a tonne. For 1 mm — about 127 m², for 2 mm — 63 m², for 5 mm — 25 m², for 10 mm — 13 m².
What is the density of stainless steel?
For calculations, 7.9 g/cm³ is assumed. Austenitic grades 304, 316 and 12Х18Н10Т give similar values. Ferritic and duplex grades have a slightly different density, so for high accuracy take the value from the certificate.
Why does the actual weight differ from the calculated one?
Because the formula calculates from nominal dimensions, while rolled steel has a tolerance on thickness and diameter. The actual length and the curvature add to the difference as well. On large batches the discrepancy is measured in percentages, not in grams.
Calculate the volume and place an order
Convert the length in metres into tonnes once — then an order on the GCX exchange operates with a clear volume. The catalogue includes sheet 0.8–10 mm, round pipe ⌀16–108 and profile pipe, round bar and angle of grades AISI 201, 304, 316L and 430.