Steel Plate Weight Calculator

A steel plate is a prism of constant thickness, so its weight is the volume times the density:

W = ρ · A · t

where ρ is the material density (7850 kg/m³ for carbon steel), A is the plane face area of the plate, and t is the thickness. Keep the units tidy and two shortcuts fall out that every estimator uses:

• Plate unit weight (per square metre): kg/m² = ρ · t / 1000 = 7.85 · t for carbon steel with t in millimetres. A 10 mm plate weighs 78.5 kg for every square metre of surface — thickness in mm × 7.85 and you are done.
• Weight of one plate: W (kg) = face area (m²) × (7.85 · t). Multiply by the number of pieces for the shipping weight, the crane pick weight or the tonnage on your quote.

The calculator handles the three plate geometries you actually cut:

• Rectangular sheet — A = L · W (the classic mill plate).
• Circular disc / blank — A = (π/4) · ⌀² (end caps, base circles, cover plates).
• Circular ring — A = (π/4) · (⌀ₒ² − ⌀ᵢ²) (flange blanks, washers, spacer rings).

Every entry is drawn as a dimensioned plan and an edge elevation carrying the thickness, so what you priced is exactly what you will fabricate. Math stays in SI internally; the SI/imperial toggle converts every dimension and every weight — plate sizes in millimetres or inches, results in kg, tonnes or pounds.

The most-searched plate question is the ms plate weight (mild-steel plate). The formula is direct:

MS plate weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.85

That constant 7.85 is the plate unit weight in kg/m² per millimetre of thickness (carbon steel, ρ = 7850 kg/m³). Quick reference for the common mill thicknesses:

Worked number — the standard 2000 × 1000 × 9.5 mm MS sheet: 2.0 × 1.0 × 9.5 × 7.85 = 149.15 kg (328.8 lb). That is the value pre-loaded when the page opens, with zero clicks. For imperial stock, an 8 ft × 4 ft × ¼″ plate (2438 × 1219 × 6.35 mm) comes out at 148.2 kg (326.7 lb).

Round blanks are everywhere — pipe caps, tank ends, bearing plates, flange blanks — and the same ρ·A·t identity handles them once the face area is the area of a circle (or an annulus):

• Circular disc: W = (π/4) · ⌀² · t · ρ. With the diameter ⌀ in metres and the plate unit weight 7.85·t, this is just face area × unit weight. A ⌀1000 × 10 mm steel disc has a face area of π/4 × 1² = 0.7854 m², so W = 0.7854 × 78.5 = 61.65 kg.
• Circular ring (annulus): W = (π/4) · (⌀ₒ² − ⌀ᵢ²) · t · ρ — subtract the hole. A ⌀500 / ⌀300 × 12 mm ring has a net area of π/4 × (0.5² − 0.3²) = 0.1257 m², giving W = 0.1257 × 94.2 = 11.84 kg. This is exactly the flange-blank or bolt-ring calculation, without hand-subtracting the bore.

Pick Circular disc or Circular ring in the shape toggle, type the diameters, and the plan view shows the true circle with its centre marks and the edge strip shows the thickness — the same drawing you would hand a laser or plasma shop.

Plate is not rolled to arbitrary thicknesses. Order a "9 mm" plate and the mill will supply 9.5 mm (or 10 mm) and charge you for it — so a weight computed on a non-stock thickness is a weight you will never be invoiced. The calculator ships a catalog of 26 commercial thicknesses:

• Metric (mm): 3, 4, 4.75, 5, 6, 8, 9.5, 10, 12, 12.5, 16, 19, 20, 22, 25, 32, 40, 50 — the round plate gauges sold across most of the world.
• Imperial (fractional inch, exact mm): 3⁄16″ = 4.7625, ¼″ = 6.35, 5⁄16″ = 7.9375, 3⁄8″ = 9.525, ½″ = 12.7, 5⁄8″ = 15.875, ¾″ = 19.05, 1″ = 25.4.

Tap any chip to snap the thickness to that stock value; type a free number and the tool tells you the nearest commercial thickness so you can round to what the supplier keeps in the rack. The metric and imperial equivalences also settle the recurring confusion between a metric 9.5 mm plate and a 3⁄8″ (9.525 mm) plate, or a metric 12.5 mm and a ½″ (12.7 mm) plate — a 0.2–0.3 mm difference that still moves the invoice on a big package.

A weight calculator tells you the tonnage; it does not tell you whether the plate is thick enough. This one does. Open "Design this as a column base plate" and the tool crosses from arithmetic into structural design:

• Inherit the footprint from a real section. Pick a column from the 1309-profile catalog (W / HEB / HSS / pipe, BR · AISC · EN · IS) and the plate L × W is set to cover the profile plus a bolt edge distance on every side — the same rule NBR 8800 and AISC Design Guide 1 use to lay out anchors. No more guessing plate sizes.
• Pre-dimension the thickness to code. Enter the factored axial load Pu, the plate grade (Fy) and the concrete class (f'c) and the plate is checked to AISC 360-J8 / AISC DG-1 — the closed form NBR 8800 shares: bearing on concrete (φc·Pp = φc·0.85·f'c·A₁·√(A₂/A₁)) and cantilever bending of the plate overhang (t ≥ ℓ·√(2·fp/(0.9·Fy)), with ℓ = max(m, n, λn')). You get the required thickness, the next commercial plate, a bearing PASS/FAIL and the governing cantilever — live.
• Snap the plate to the answer. One tap sets the calculator's thickness to the code value, so the weight you export is the weight of a plate that actually passes.
• Hand it to the solver. "Design in the 3D editor" builds the plate as a real column base — a fixed-footing column on your chosen section, loaded with Pu — and opens it in the free CalcSteel editor. There the FEM finds the true reaction and the base-plate overlay verifies plate thickness, bearing and anchors against it. The plate flows plate → column base → FEM reactions → NBR 8800 / AISC 360 check, not a dead number. No free tool (SkyCiv free, Omni, calcresource) sizes the plate to code, let alone drops it into a solver.

Real jobs are never one plate. Switch to the Plate list tab for a mini take-off: each line carries a description, a shape, its dimensions, a thickness and a quantity, and the running total in kg, tonnes and lb updates as you type — mixing rectangular plates, discs and rings freely in one sheet. Push whatever is in the Single-plate tab straight into the list with Add to plate list.

• Plates per tonne. For a single plate the results card shows how many identical plates make one metric tonne — the number you quote to a mill that sells by the tonne, and the sanity check that catches a wrong thickness at a glance.
• Optional price per kg (R$, $, € or £) turns every line and the grand total into a cost — steel is sold by weight, so the weight sheet becomes a budget sheet.
• Export CSV — free, no login. The file opens directly in Excel or Google Sheets with item, shape, dimensions, thickness, face area, weight-each, quantity, total weight and cost columns — ready to attach to a proposal or import into your ERP.
• Share the whole calculation as a link. Shape, dimensions, thickness, material, price and the entire plate list serialize into the URL, so you can paste the finished take-off straight into the project group chat.

The natural workflow: size a plate → tap the stock thickness → Add to plate list → repeat → export. It takes seconds and costs nothing.

Carbon-steel plate is standardized at ρ = 7850 kg/m³ (490 lb/ft³, 78.5 kN/m³ specific weight) — the value used by NBR 8800, AISC 360 and Eurocode 3. Alloy changes it a little for stainless and a lot for aluminium, and the plate unit weight scales in exactly the same ratio:

* The zinc coating adds a small mass on top of the base plate (roughly 1–6 % depending on coating class and thickness); enter a custom density if your spec requires it. Pick the material in the dropdown — or type any custom density — and the same 2000 × 1000 × 9.5 mm plate that weighs 149.15 kg in mild steel becomes 152.0 kg in 304 stainless and 51.3 kg in 6061 aluminium, instantly.