Calculators
Weight, container loading and panel quantities — the three sums every steel order starts with.
Calculators
Looking for load tables, container quantities or product comparisons instead? Those are in the guides.
Steel grades
Chemistry, mechanical properties and equivalents of every grade we supply (S235JR, S355J2, DX51D, 304, 316, P265GH …) are documented on our reference site steelstandart.com.
One relation behind all of them
Every calculator here is the same physics: weight = volume × density, with steel at 7.85 kg/dm³. What changes between them is only how the cross-section is worked out.
Flat product collapses to a single line — thickness in millimetres × 7.85 gives kilograms per square metre. A sandwich panel adds two facings and a core of known density. A container calculation is a packing problem rather than a weight one, bounded by payload at one end and by internal volume at the other.
None of it is proprietary and all of it can be checked by hand, which is the point: a number you cannot verify is a number you cannot put on an order.
Where a calculator stops being right
Three cases, and all three are common.
Rolled sections have root radii and fillets that no product of dimensions reproduces. Their mass comes from the catalogue, not from a formula, which is why the size tables exist.
Cold-formed hollow sections have corner radii of roughly twice the wall thickness, so a sharp-cornered calculation overstates the mass by 2–4 % on thin walls.
Coated material carries zinc or paint that the steel density does not account for: 3–6 % on thin hot-dip galvanized sections, and about 275 g/m² for a Z275 coil coating.
None of these matter for a truckload estimate. All of them matter on a purchase order.
From a calculated weight to a real order
The calculated figure is the theoretical weight, and for rolled and formed products that is what gets invoiced — mills bill on catalogue mass, not on the weighbridge, because rolling tolerance makes any other basis unworkable.
What still has to be added is the allowance. Five to eight per cent over the theoretical weight covers kerf and skeleton on simple rectangular nesting; twelve to fifteen where the nest is complex or the sheet size is fixed. On roofing, three to five per cent for a simple rectangular roof and eight to ten where the plan is cut up, plus the end laps.
Buying to exact theoretical weight is the reliable way to end up one sheet short.
Frequently asked questions
How do I calculate steel plate weight?
Thickness in millimetres × 7.85 gives kilograms per square metre; multiply by the area. A 10 mm plate of 2 × 1 m is 10 × 7.85 × 2 = 157 kg. The same relation underlies every flat-product calculation on the site.
Is the calculated weight what I will be invoiced?
For rolled and formed products, yes. The trade bills on theoretical weight — catalogue mass times length times quantity — because rolling tolerance makes a weighbridge basis impractical for both sides.
Why does my hollow section come out heavier than the catalogue?
The simple formula assumes sharp corners. A cold-formed section has an outside corner radius of about twice the wall thickness, and that missing material is 2–4 % on thin walls. Catalogue values include the correction.
How much waste should I allow?
Five to eight per cent over theoretical weight for simple rectangular nesting, twelve to fifteen for complex nests or fixed sheet sizes. On roofing, three to five per cent on a simple roof and eight to ten where the plan is cut up, plus laps.
Do the calculators account for galvanizing?
The zinc is a separate allowance. Hot-dip galvanizing after fabrication adds 3–6 % on thin sections and less on heavy ones; a Z275 continuous coating adds about 275 grams per square metre of coil surface.