Quick reference
| Thickness (mm) | Plate (kg/m²) |
|---|---|
| 3 | 23.55 |
| 4 | 31.4 |
| 5 | 39.25 |
| 6 | 47.1 |
| 8 | 62.8 |
| 10 | 78.5 |
| 12 | 94.2 |
| 15 | 117.75 |
| 20 | 157 |
| 25 | 196.25 |
| 30 | 235.5 |
| 40 | 314 |
| 50 | 392.5 |
Key points
- Plate: thickness (mm) × 7.85 = kg/m².
- Flat bar: width × thickness (mm) × 0.00785 = kg/m.
- All figures use 7,850 kg/m³, the usual density for carbon steel.
- Order sheet by millimetres: gauge numbers differ between systems.
Terms explained in the A–Z glossary.
Download
Two-page summary of the figures on this page, with sources. Free to share with credit to Koyda Ltd.
Flat bar weight (kg/m)
Width down the side, thickness across the top, both in mm.
| Width | 5mm | 6mm | 8mm | 10mm | 12mm | 15mm | 20mm | 25mm |
|---|---|---|---|---|---|---|---|---|
| 25 | 0.98 | 1.18 | 1.57 | 1.96 | 2.35 | 2.94 | 3.92 | 4.91 |
| 30 | 1.18 | 1.41 | 1.88 | 2.35 | 2.83 | 3.53 | 4.71 | 5.89 |
| 40 | 1.57 | 1.88 | 2.51 | 3.14 | 3.77 | 4.71 | 6.28 | 7.85 |
| 50 | 1.96 | 2.35 | 3.14 | 3.92 | 4.71 | 5.89 | 7.85 | 9.81 |
| 60 | 2.35 | 2.83 | 3.77 | 4.71 | 5.65 | 7.06 | 9.42 | 11.77 |
| 65 | 2.55 | 3.06 | 4.08 | 5.10 | 6.12 | 7.65 | 10.20 | 12.76 |
| 75 | 2.94 | 3.53 | 4.71 | 5.89 | 7.06 | 8.83 | 11.77 | 14.72 |
| 80 | 3.14 | 3.77 | 5.02 | 6.28 | 7.54 | 9.42 | 12.56 | 15.70 |
| 90 | 3.53 | 4.24 | 5.65 | 7.06 | 8.48 | 10.60 | 14.13 | 17.66 |
| 100 | 3.92 | 4.71 | 6.28 | 7.85 | 9.42 | 11.77 | 15.70 | 19.62 |
| 120 | 4.71 | 5.65 | 7.54 | 9.42 | 11.30 | 14.13 | 18.84 | 23.55 |
| 150 | 5.89 | 7.06 | 9.42 | 11.77 | 14.13 | 17.66 | 23.55 | 29.44 |
| 200 | 7.85 | 9.42 | 12.56 | 15.70 | 18.84 | 23.55 | 31.40 | 39.25 |
Sheet gauges (SWG) to mm
| SWG | Inch | mm | Steel kg/m² |
|---|---|---|---|
| 8 | 0.160 | 4.064 | 31.90 |
| 10 | 0.128 | 3.251 | 25.52 |
| 11 | 0.116 | 2.946 | 23.13 |
| 12 | 0.104 | 2.642 | 20.74 |
| 13 | 0.092 | 2.337 | 18.35 |
| 14 | 0.080 | 2.032 | 15.95 |
| 16 | 0.064 | 1.626 | 12.76 |
| 18 | 0.048 | 1.219 | 9.57 |
| 20 | 0.036 | 0.914 | 7.17 |
| 22 | 0.028 | 0.711 | 5.58 |
| 24 | 0.022 | 0.559 | 4.39 |
Imperial Standard Wire Gauge values. US and manufacturers' sheet gauges differ, so always confirm the thickness in mm.
Calculate any size
Use the steel weight calculator in plate mode for any length, width, thickness and quantity, with an optional price per tonne.
Frequently asked questions
How do I calculate the weight of steel plate?
Multiply length × width × thickness (all in metres) by 7,850 kg/m³. In practice: thickness in mm × 7.85 gives kg per square metre. A 2,500 × 1,250 × 10mm sheet is 3.125 m² × 78.5 = 245.3 kg.
How much does 100 × 10 flat bar weigh?
7.85 kg per metre: 100 × 10 × 0.00785. A 6m length weighs 47.1 kg.
What thickness is 16 gauge steel?
On the Imperial Standard Wire Gauge (SWG), 16 gauge is 0.064 inch, which is 1.626mm. Other gauge systems give slightly different values, so order sheet by thickness in millimetres.
Why does my plate weigh more than the table?
Plate is rolled to thickness tolerances, so actual weight varies a little from nominal. Coatings such as galvanising also add weight. Use nominal weights for estimating and the delivery note or weighbridge for actual weight.
Sources
- BS EN 1991-1-1 Annex A: density of steel 77–78.5 kN/m³ (BSI); 7,850 kg/m³ is the usual design density
- Standard wire gauge (Imperial Standard Wire Gauge, 1884): gauge to inch and mm values (Wikipedia)
General guidance only, not design advice for a specific project. Building regulations guidance changes: check the current edition of each document, and get project-specific design from a competent engineer. Koyda Ltd accepts no liability for decisions made using this page.