--- title: Steel Plate & Flat Bar Weight Tables (kg/m², kg/m) + SWG | Koyda url: https://www.koyda.com/guides/plate-and-flat-bar-weights/ description: Steel plate weight per m² by thickness, flat bar weight per metre by width and thickness, and sheet gauge (SWG) to mm conversion, at 7,850 kg/m³. last_modified: 2026-10-11 publisher: Koyda Ltd, Units 27–29 Jesmor Farm, St Piers Lane, Lingfield, Surrey RH7 6PN. 07753 213617, joe@koyda.com --- Technical guide # Steel Plate and Flat Bar Weight Tables Weight per square metre for steel plate, weight per metre for flat bar, and sheet gauges converted to millimetres. All figures use 7,850 kg/m³. Last reviewed 11 October 2026 · Koyda Ltd Quick answer Steel plate weighs 7.85 kg per square metre for every millimetre of thickness, so 10mm plate is 78.5 kg/m². Flat bar weighs width × thickness × 0.00785 kg per metre (in mm), so 100 × 10 flat is 7.85 kg/m. These are nominal weights at 7,850 kg/m³ and exclude rolling tolerances and coatings. Cite this: Koyda Ltd, “Steel Plate and Flat Bar Weight Tables”, https://www.koyda.com/guides/plate-and-flat-bar-weights/, reviewed 11 October 2026. ## 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](https://www.koyda.com/guides/glossary/). Download [Quick reference PDF ↓](https://www.koyda.com/downloads/koyda-plate-flat-bar-weights-quick-reference.pdf) 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](https://www.koyda.com/steel-weight-calculator/?m=plate&pl=1000&pw=1000&pt=10&pq=1#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 1. 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 2. [Standard wire gauge (Imperial Standard Wire Gauge, 1884): gauge to inch and mm values (Wikipedia)](https://en.wikipedia.org/wiki/Standard_wire_gauge) 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. ContentsGuide 1. [Quick reference](#quick) 2. [Flat bar weight (kg/m)](#flat) 3. [Sheet gauges (SWG) to mm](#gauges) 4. [Calculate any size](#calc) 5. 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