Steel plate weighs 7.85 kg per square metre for every millimetre of thickness, so plate weight in kg = length (m) x width (m) x thickness (mm) x 7.85. A 10 mm plate weighs 78.5 kg/m², a 20 mm plate 157 kg/m², and in imperial terms plate weighs about 40.8 lb per square foot per inch of thickness. The charts below give weights by thickness, whole-sheet weights and the adjustments for holes and round plates, so you can weigh anything from a base plate to a full sheet.
The plate weight formula
Everything comes from the density of carbon steel, which is taken as about 7,850 kg per cubic metre. A plate one metre square and one millimetre thick has a volume of 0.001 m³, so it weighs 7.85 kg. That gives the working formulas:
Metric: weight (kg) = L (m) x W (m) x t (mm) x 7.85
Metric, all in millimetres: weight (kg) = L x W x t x 0.00000785
Imperial: weight (lb) = L (ft) x W (ft) x t (in) x 40.8
The imperial factor comes from steel weighing about 0.2836 lb per cubic inch: 144 square inches in a square foot, times one inch, times 0.2836 = 40.8 lb.
Example. A 600 mm x 400 mm plate, 12 mm thick:
0.6 x 0.4 x 12 x 7.85 = 22.6 kg (about 49.8 lb)
The same density applies to every carbon steel plate grade, so a 350W plate weighs the same as a 300W or A36 plate of the same size. Stainless steel and aluminium have different densities, so these numbers do not apply to them.
Steel plate weight chart: metric thicknesses
| Thickness | kg/m² | kg/ft² | lb/ft² |
|---|---|---|---|
| 3 mm | 23.6 | 2.19 | 4.8 |
| 5 mm | 39.3 | 3.65 | 8.0 |
| 6 mm | 47.1 | 4.38 | 9.6 |
| 8 mm | 62.8 | 5.83 | 12.9 |
| 10 mm | 78.5 | 7.29 | 16.1 |
| 12 mm | 94.2 | 8.75 | 19.3 |
| 15 mm | 117.8 | 10.94 | 24.1 |
| 16 mm | 125.6 | 11.67 | 25.7 |
| 20 mm | 157.0 | 14.59 | 32.2 |
| 25 mm | 196.3 | 18.23 | 40.2 |
| 30 mm | 235.5 | 21.88 | 48.2 |
| 40 mm | 314.0 | 29.17 | 64.3 |
| 50 mm | 392.5 | 36.46 | 80.4 |
Calculated from 7,850 kg/m³.
Steel plate weight chart: imperial thicknesses
Much of the plate sold in Canada is rolled to fractional-inch thicknesses, and drawings often show the converted metric value (for example 12.7 mm for 1/2 in).
| Thickness (in) | Thickness (mm) | kg/m² | lb/ft² |
|---|---|---|---|
| 1/8 | 3.2 | 24.9 | 5.1 |
| 3/16 | 4.8 | 37.4 | 7.7 |
| 1/4 | 6.4 | 49.8 | 10.2 |
| 5/16 | 7.9 | 62.3 | 12.8 |
| 3/8 | 9.5 | 74.8 | 15.3 |
| 1/2 | 12.7 | 99.7 | 20.4 |
| 5/8 | 15.9 | 124.6 | 25.5 |
| 3/4 | 19.1 | 149.5 | 30.6 |
| 7/8 | 22.2 | 174.5 | 35.7 |
| 1 | 25.4 | 199.4 | 40.8 |
| 1-1/4 | 31.8 | 249.2 | 51.1 |
| 1-1/2 | 38.1 | 299.1 | 61.3 |
| 2 | 50.8 | 398.8 | 81.7 |
Calculated from 7,850 kg/m³ (0.2836 lb/in³).
Note that 12 mm and 1/2 in are not the same plate: 1/2 in is 12.7 mm, about 6% thicker and heavier. If a drawing calls for a metric thickness and the supplier offers the nearest imperial one, that substitution is the designer's decision. Our guide to ordering plate cut to size covers grades and thicknesses in more detail.
Weight of full sheets
Plate is commonly sold in full sheets such as 4 x 8 ft, 5 x 10 ft and 8 x 20 ft. These weights help when planning how a load will be lifted and moved.
| Thickness | 4 x 8 ft sheet | 5 x 10 ft sheet | 8 x 20 ft sheet |
|---|---|---|---|
| 3/16 in (4.8 mm) | 111 kg (245 lb) | 174 kg (383 lb) | 556 kg (1,225 lb) |
| 1/4 in (6.4 mm) | 148 kg (327 lb) | 232 kg (511 lb) | 741 kg (1,634 lb) |
| 3/8 in (9.5 mm) | 222 kg (490 lb) | 347 kg (766 lb) | 1,111 kg (2,450 lb) |
| 1/2 in (12.7 mm) | 296 kg (653 lb) | 463 kg (1,021 lb) | 1,482 kg (3,267 lb) |
| 3/4 in (19.1 mm) | 445 kg (980 lb) | 695 kg (1,532 lb) | 2,223 kg (4,901 lb) |
| 1 in (25.4 mm) | 593 kg (1,307 lb) | 926 kg (2,042 lb) | 2,964 kg (6,534 lb) |
Even a 4 x 8 sheet of 1/4 in plate is too heavy to handle safely by hand. Full sheets move with a forklift, a crane and plate clamps, or a vacuum lifter. Sizes and availability vary by supplier, so these are for weight planning, not a stock list.
Base plates, round plates and holes
Most fabricated plate parts are small, but the same formula applies.
Square and rectangular base plates. A 300 x 300 mm base plate at 19.1 mm (3/4 in):
0.3 x 0.3 x 19.1 x 7.85 = 13.5 kg
Round plates. Use the area of a circle: weight (kg) = 3.1416 x r² (m) x t (mm) x 7.85. A 400 mm diameter flange 25.4 mm thick:
3.1416 x 0.2 x 0.2 x 25.4 x 7.85 = 25.1 kg
Holes. Each hole removes a small cylinder: weight removed (kg) = 3.1416 x d² / 4 (mm²) x t (mm) x 0.00000785. A 27 mm hole through a 19.1 mm plate removes about 0.09 kg. Four of them take the 13.5 kg base plate above down to about 13.2 kg. For estimating, holes can usually be ignored. For a large run of heavily drilled plates, deduct them.
Plates with copes, chamfers or cut-outs. Work out the gross rectangle, then subtract the area removed. If you have a DXF, the CAD software will report the area directly; multiply it by the thickness and 7.85.
For what the plate size and thickness should be in the first place, see our base plate size and thickness chart.
Worked examples
Stair landing plate. A 1,200 x 1,500 mm plate, 6.4 mm (1/4 in):
1.2 x 1.5 x 6.4 x 7.85 = 90.4 kg
That is a two-person lift at minimum, more if it has to go up stairs. Checker plate (tread plate) is a little heavier than smooth plate of the same nominal thickness because of the raised pattern; see our guide to steel checker plate.
A batch of connection plates. Forty shear tabs, each 100 x 250 mm, 9.5 mm (3/8 in):
- One plate: 0.1 x 0.25 x 9.5 x 7.85 = 1.86 kg
- Forty plates: about 75 kg
A trench cover. A 1,000 x 2,400 mm plate, 25.4 mm (1 in):
1.0 x 2.4 x 25.4 x 7.85 = 479 kg
At that weight, the lifting gear, the pick points and the ground under the equipment all need planning.
Why the scale reading may differ
Calculated weights are nominal. Real plate can differ slightly because:
- Rolling tolerances. Plate thickness and flatness vary within the tolerances of the material standard, and plate can run slightly over nominal thickness.
- Cut edges. Torch, plasma and waterjet cuts remove a kerf, so the cut piece is marginally smaller than the drawing dimension plus the kerf.
- Coatings. Primer adds almost nothing. Hot-dip galvanizing adds a zinc layer that is noticeable on thin plate and large orders.
- Rounding. Tables round to one decimal, and converted imperial thicknesses pick up small differences.
For shipping and lifting, use the calculated weight plus a sensible margin. For how plate is priced, which is partly by weight and partly by the work done on it, see steel plate prices in Canada, and for shapes other than plate, how to calculate structural steel weight.
Plate cut and drilled to your details
We cut and drill base plates, cap plates and connection plates to your details, and weld them to posts, beams and columns in our CWB certified shop. Send a drawing, a DXF or a plate schedule and we'll quote the plates on their own or with the rest of your steel.
Request a quote for your plates, or see the steel products we supply and fabricate.
Frequently asked questions
How do you calculate steel plate weight?
Multiply length (m) x width (m) x thickness (mm) x 7.85 to get kilograms. A 1,000 mm x 500 mm plate 10 mm thick weighs 1.0 x 0.5 x 10 x 7.85 = 39.3 kg. In imperial, multiply square feet by thickness in inches by 40.8 to get pounds.
What is the density of steel plate?
Carbon steel plate is taken as about 7,850 kg per cubic metre (about 0.284 lb per cubic inch, or 490 lb per cubic foot). That is where the 7.85 kg per square metre per millimetre of thickness comes from.
How much does a 4 x 8 sheet of 1/4 inch steel plate weigh?
About 148 kg (327 lb). A 4 x 8 ft sheet is 32 square feet, and 1/4 inch plate weighs about 10.2 lb per square foot.
How much does 1 inch steel plate weigh per square foot?
About 40.8 lb per square foot, or about 199 kg per square metre at 25.4 mm thick.
