Steel Plate Weight Calculator
Enter the length, width and thickness of your steel plate, choose the alloy, and the calculator gives you the weight per plate plus the total weight for any quantity. Switch between metric and imperial units. Supports carbon steel, stainless steel, galvanized, tool steel, and custom density.
Formula
Worked example
A mild steel (7870 kg/m3) rectangular plate 2000 mm x 1000 mm x 10 mm thick: Area = 2.000 m x 1.000 m = 2.000 m2. Volume = 2.000 m2 x 0.010 m = 0.020000 m3. Weight = 0.020000 x 7870 = 157.40 kg (347.01 lb).
Steel plate weight formula
The weight of a steel plate is its volume multiplied by the density of the alloy. For a rectangular plate: Weight (kg) = Length (m) x Width (m) x Thickness (m) x Density (kg/m3). For a circular plate: Weight (kg) = pi x (Diameter/2)^2 x Thickness (m) x Density (kg/m3). In practice you can also use the surface weight method: Weight (kg) = Area (m2) x Thickness (mm) x Density (kg/m3) / 1000. All three approaches give the same answer. The surface weight per m2 for mild steel plate is simply thickness in mm multiplied by 7.87 kg/m2/mm - so a 10 mm mild steel plate weighs 78.7 kg/m2.
Steel alloy densities and how they affect plate weight
The density of steel varies between alloys but stays within a fairly tight band. Mild steel and carbon steel sit around 7830-7870 kg/m3. Stainless steel grades are denser, from 7900 to 8030 kg/m3 for 304 and 316 respectively, so a same-size stainless plate is about 2-3% heavier than mild steel. Tool steel at around 7715 kg/m3 is slightly lighter. Galvanized plates share the same base density as carbon steel since the zinc coating adds negligible mass for standard coating weights. If you are working with a specialist alloy not in the list, enter a custom density - your mill certificate or material datasheet will give the exact figure.
How to account for holes and cutouts
When a plate has a hole punched or drilled through it, the volume of the removed cylinder must be deducted. For a single circular hole of diameter d: Deducted weight = pi x (d/2)^2 x thickness x density. This calculator handles one central hole automatically via the optional hole diameter field. For plates with multiple holes or complex shapes, calculate the area of each cutout separately and subtract. Fabricators often add around 2-5% for weld preparation losses and shop tolerances, so the theoretical calculated weight is a floor, not a ceiling.
Practical uses and ordering tips
Structural steel is typically ordered by weight (tonnes) or by area (m2 at a specified thickness). Knowing both lets you cross-check supplier quotes. The surface weight column in the reference table below is particularly useful: multiply kg/m2 by your required area and you have a fast estimate without entering full dimensions. For large orders, rounding up to the nearest standard mill cut size (e.g. 2400 x 1200 mm or 3000 x 1500 mm) often reduces waste. Always verify with your structural engineer for load-bearing applications - this calculator gives theoretical material weight, not structural capacity.
Common mild steel plate weights by thickness (kg/m²)
| Thickness (mm) | Weight (kg/m²) | Weight (lb/ft²) |
|---|---|---|
| 3 | 23.61 | 4.84 |
| 5 | 39.35 | 8.06 |
| 6 | 47.22 | 9.68 |
| 8 | 62.96 | 12.9 |
| 10 | 78.7 | 16.13 |
| 12 | 94.44 | 19.36 |
| 16 | 125.92 | 25.81 |
| 20 | 157.4 | 32.25 |
| 25 | 196.75 | 40.31 |
| 32 | 251.84 | 51.6 |
| 40 | 314.8 | 64.51 |
| 50 | 393.5 | 80.64 |
| 100 | 787 | 161.27 |
Surface weight for mild steel (7870 kg/m³). Multiply by your plate area in m² to get the weight.
Frequently asked questions
How do I calculate the weight of a steel plate?
Multiply the plate dimensions (length x width x thickness) to get the volume in cubic metres, then multiply by the density of the steel alloy in kg/m3. For mild steel (7870 kg/m3) a 2000 mm x 1000 mm x 10 mm plate is 0.02 m3 in volume, giving 0.02 x 7870 = 157.4 kg. A quick shortcut for mild steel is: weight per m2 = thickness in mm x 7.87.
What density should I use for steel plate?
The density depends on the alloy. Mild steel is about 7870 kg/m3, standard carbon steel 7840 kg/m3, stainless 304 around 8000 kg/m3, and stainless 316 about 8030 kg/m3. Most structural calculations use 7850 kg/m3 as a conservative round figure that works for the majority of common steel grades.
How heavy is a 10 mm mild steel plate per square metre?
A 10 mm mild steel plate (density 7870 kg/m3) weighs 10 x 7.870 = 78.70 kg/m2. For a 2 m x 1 m plate that is 78.70 x 2 = 157.40 kg. The reference table in this calculator lists surface weights for common thicknesses from 3 mm to 100 mm.
Does a hole significantly reduce the plate weight?
Yes, but the effect depends on the hole-to-plate area ratio. A 100 mm diameter hole in a 1000 mm x 1000 mm plate removes only 0.785% of the area, so for most structural plates a single bolt hole is negligible. However, large man-way openings or multiple cutouts can reduce mass by 10-30%, making an accurate deduction worthwhile for ordering and lifting calculations.
Is stainless steel plate heavier than mild steel plate?
Yes, by a small amount. Stainless 304 is about 8000 kg/m3 versus mild steel at 7870 kg/m3, a difference of roughly 1.7%. Stainless 316 at 8030 kg/m3 is about 2.0% heavier. For most practical purposes the difference is minor, but it adds up on large fabrications.
How do I convert the weight from kg to metric tons?
Divide kilograms by 1000. A plate weighing 1574 kg is 1.574 metric tons (tonnes). The calculator shows the total weight in both kg and metric tons when quantity is entered.