EN 10029 Steel Plate Tolerances: Thickness, Width, Length & Flatness

EN 10029 sets the tolerances on dimensions and shape for hot-rolled steel plate 3 mm thick and above. Its central feature is a choice: the purchaser selects one of four thickness tolerance classes, A, B, C or D, at the time of enquiry and order, and class A applies by default if none is stated. The four classes share the same total permitted span at any given thickness. What changes between them is where that span sits relative to the nominal thickness.

That is the practical point for anyone estimating weight. Choosing class C does not make the plate more accurate; it moves the whole band above nominal so that no plate is ever thinner than ordered.

Scope: what EN 10029 covers and what it does not

The standard applies to hot-rolled non-alloy and alloy steel plates with:

• nominal thickness from 3 mm to 400 mm inclusive
• nominal width of 600 mm or more

Below 600 mm wide, tolerances for material cut or slit from plate are agreed between manufacturer and purchaser.

The exclusions matter as much as the scope. EN 10029:2010 states that it does not apply to stainless steels, and that it does not cover round plates, custom-made plates, chequer or bulb plate for flooring, or wide flats.

Two of those are worth flagging because they are commonly assumed the other way round. Stainless plate is outside the standard’s scope despite EN 10029 being widely quoted for it. And chequer plate is excluded, so the class A to D structure does not govern patterned floor plate; checkered steel plate weight covers how that product is specified instead.

The current edition at the time of writing is EN 10029:2010, published as BS EN 10029:2010 with a corrigendum in January 2012, superseding EN 10029:1991. Confirm the current status before relying on it for a contract. One change between editions is directly relevant here: the 1991 edition was titled “Tolerances on dimensions, shape and mass” and the 2010 edition is titled “Tolerances on dimensions and shape”. Mass tolerances were removed.

That removal is why a 2010-compliant plate order carries no tolerance on weight at all. Weight follows from the delivered dimensions, and nothing in the standard caps it directly.

The four thickness tolerance classes

At enquiry and order the purchaser indicates which class is required. The standard defines them by how the minus side behaves:

• Class A: minus tolerance depending on the nominal thickness
• Class B: a fixed minus tolerance of 0,3 mm
• Class C: a fixed minus tolerance of 0,0 mm
• Class D: symmetrical tolerances

If no class is stated on the order, class A applies.

The classes have the same span

Work the tolerance values for a single thickness band through a weight calculation and the structure becomes obvious.

Known values: 20 mm × 2500 mm × 6000 mm carbon steel at 7,850 kg/m³. Area 15.00 m², so each millimetre of thickness is 15.00 × 7.85 = 117.75 kg. Theoretical weight 2,355.0 kg (5,192 lb).

Result: every class spans 1.6 mm, which is 188.4 kg, or 8.00% of the nominal weight. Interpretation: the class does not buy precision. It buys a position. Reverse check: 1.6 mm × 117.75 kg per mm = 188.4 kg, and 188.4 ÷ 2,355.0 = 8.00%.

Class D is the only one centred on nominal, so it is the only one where the theoretical weight is an unbiased estimate of the delivered weight. Class C sits entirely above nominal, which guarantees the material but guarantees an overweight delivery with it. Class A, the default, is biased upwards but less so.

The thickness limits used here are those tabulated for the 15 mm to under 25 mm band. Read the values for your own thickness band from the current edition, because the band boundaries and the values inside them are what govern the order.

Choosing a class by what it is for

Each class exists for a different reason, and none is simply better.

Class A is the default and the general-purpose choice. Its minus tolerance grows with thickness, which reflects what a mill can realistically hold. If nothing on the order says otherwise, this is what arrives.

Class B fixes the minus tolerance at 0,3 mm regardless of thickness. On heavy plate that is a much tighter minus limit than class A allows, so it is the choice where a minimum wall or a minimum section matters and the plate is thick.

Class C permits nothing under nominal. Every plate is at least the ordered thickness. This is the class to specify when the design depends on a guaranteed minimum thickness, for corrosion allowance, for machining stock, or where a code requires it. It costs more, and it makes the delivered weight systematically higher than the theoretical figure, because the entire permitted band now sits above nominal.

Class D is symmetrical. It is the class that makes calculated weight the best single estimate of delivered weight, because the band is centred on nominal. Where an order is being priced on theoretical weight and both parties want that figure to be a fair midpoint, class D is the one that makes it so.

There is a clean way to summarise the trade-off. Class C guarantees material. Class D guarantees that the theoretical weight is unbiased. They are different goals and they point at different classes.

Where thickness is measured

EN 10029 specifies the measurement location, and it is not the same rule as ASTM A6/A6M uses.

Thickness shall be measured at any point more than 25 mm from the transverse or longitudinal edges of the plate, other than locally ground areas. For plates with untrimmed edges, the measuring points are agreed at the time of enquiry and order.

The standard also limits the maximum thickness difference within a single plate, in a table indexed by nominal thickness and nominal width. That is a separate requirement from the tolerance on nominal thickness: a plate can be inside its class limits at every point and still fail if the variation across it is too large.

Compare that with ASTM A6/A6M, which requires the measurement 3/8 to 3/4 in (10 to 20 mm) from the longitudinal edge specifically, and applies a 1¾ multiplier if it is taken elsewhere. Two standards, two different measurement regimes, two different numbers from the same plate. ASTM A6/A6M thickness tolerances covers the North American structure in full.

Width and length

Both are one-sided. Nothing under the specified dimension is permitted, and a tabulated amount over it is.

Width, for plates with trimmed edges, is tolerated by thickness band: up to +20 mm for plate under 40 mm thick, +25 mm from 40 to under 150 mm, and +30 mm from 150 to 400 mm, with nothing under in every case. Plates supplied with untrimmed edges, condition NK, have their width tolerances agreed at order.

Length is tolerated by length band, from +20 mm on plates under 4,000 mm to +100 mm on plates from 15,000 to 20,000 mm, again with nothing under. Beyond 20,000 mm the tolerance is agreed.

Width is measured perpendicular to the major axis of the plate. Length is the length of the shorter of the two longitudinal edges.

Because both are one-sided in the same direction, they add to the thickness over-tolerance rather than cancelling it.

Worked example: the full dimensional range

Known values: 20 mm × 2500 mm × 6000 mm, class A. Width tolerance 0 to +20 mm (thickness under 40 mm). Length tolerance 0 to +40 mm (length 6,000 to under 8,000 mm).

Theoretical:

V = 0.020 × 2.500 × 6.000 = 0.300 m3
m = 0.300 × 7,850 = 2,355.0 kg (5,192 lb)

At every upper limit, 21.0 × 2520 × 6040 mm:

V = 0.0210 × 2.520 × 6.040 = 0.319636 m3
m = 0.319636 × 7,850 = 2,509.1 kg (5,532 lb)

At every lower limit, 19.4 × 2500 × 6000 mm:

V = 0.0194 × 2.500 × 6.000 = 0.291000 m3
m = 0.291000 × 7,850 = 2,284.3 kg (5,036 lb)

Result: a range from 3.00% under the theoretical weight to 6.55% over, spanning 224.8 kg or 9.55% of nominal. Interpretation: thickness supplies most of it, but width and length add 1.55 percentage points on the upper side and nothing on the lower, which is why the band is not centred even in class A. Reverse check: 1.05 × 1.008 × 1.006667 = 1.06549.

Put the nominal figures into the Steel Plate Weight Calculator for the quotation, and carry the range separately.

Shape: edge camber, out-of-squareness and flatness

EN 10029 covers shape as well as size, and the rules are worth knowing because they are stated as conditions rather than as simple numbers.

Edge camber and out-of-squareness. For plate ordered with normal edge camber and out-of-squareness, the requirement is that it must be possible to inscribe a rectangle with the ordered dimensions inside the delivered plate. That is an elegant way of stating the limit: whatever the edges do, the plate you ordered has to fit inside what arrives. Where tighter control is needed, the purchaser includes the letter G in the order designation and agrees maximum values.

Edge camber is defined as the maximum deviation between a longitudinal edge and the straight line joining its two ends, measured on the concave edge. Out-of-squareness is the orthogonal projection of one transverse edge onto one longitudinal edge.

Flatness has two classes: normal, class N, which applies unless otherwise specified, and special, class S, which is ordered by including the letter S in the designation. Deviation from flatness is measured by laying the plate on a flat surface and measuring the gap between the plate and a straight edge 1,000 mm or 2,000 mm long, placed in any direction, counting only the part between two points of contact.

The flatness tables also depend on the steel, splitting products into type L, with a specified minimum yield strength below 460 N/mm² and neither quenched nor quenched and tempered, and type H, covering higher strength and quenched and tempered products. Higher strength plate is harder to flatten, so it is allowed more deviation.

The order designation

EN 10029 provides a compact way to state all of these options in one string. The standard’s own example covers 20 plates of S235JR with 25 mm nominal thickness, class B thickness tolerance, limited edge camber and out-of-squareness, and special flatness:

20 plates EN 10029-B-G-S
25 x 2 000 x 4 500
Steel EN 10025-2 - S235JR

The letters after the standard number are the options: B for the thickness tolerance class, G for limited edge camber and out-of-squareness, S for special flatness. Add NK for untrimmed edges. Leave them out and the defaults apply: class A, trimmed edges, normal camber, normal flatness.

That string is worth using. It puts every tolerance decision on one line where it can be checked, rather than leaving them to be assumed. How to read steel plate dimensions covers the rest of what belongs on a plate order.

What the purchaser must supply

The standard lists the information the purchaser has to give at enquiry and order: the quantity to be delivered, the product form, the number of this dimensional standard, and the nominal thickness, width and length in millimetres. If that information is not given, the supplier is required to refer back rather than assume.

That list is a useful checklist in its own right. An enquiry missing any of it is not yet an enquiry.

EN 10029 FAQs

What are the four EN 10029 thickness tolerance classes? Class A has a minus tolerance that depends on nominal thickness, class B a fixed minus tolerance of 0,3 mm, class C a fixed minus tolerance of 0,0 mm, and class D symmetrical tolerances. Class A applies if the order does not state one.

Which EN 10029 class should I order? Class C where a guaranteed minimum thickness matters, class D where the theoretical weight should be an unbiased estimate of the delivered weight, class B where a tight minus limit is needed on heavy plate, and class A for general work. Each carries a different price.

Does EN 10029 apply to stainless steel plate? No. EN 10029:2010 states explicitly that it does not apply to stainless steels, despite being widely quoted for them. Confirm which dimensional standard your stainless plate is supplied to.

Does EN 10029 set a tolerance on plate weight? Not in the 2010 edition. Mass was in the title and scope of the 1991 edition and was removed in the 2010 revision, so weight now follows from the delivered dimensions rather than being limited directly.

What is the width tolerance under EN 10029? For trimmed edges, nothing under the specified width and a tabulated amount over it, stepping up with plate thickness from +20 mm through +25 mm to +30 mm. Untrimmed edge plate, condition NK, is agreed at order.

Pick the class before the price

The most useful thing about EN 10029 is that it makes the tolerance a decision rather than an outcome. Four classes, one chosen at order, with a default that applies if you say nothing.

Decide which one the job actually needs, put it in the order designation, and then calculate the weight on nominal dimensions with the Steel Plate Weight Calculator, knowing which way the band sits around the answer. For the same question under North American practice, ASTM A6/A6M has one fixed rule instead of four classes, and theoretical versus actual steel plate weight covers what the band means once the plate is on a truck.

Scope, class definitions, measurement rules, designation format and shape requirements in this article are taken from EN 10029:2010, Hot-rolled steel plates 3 mm thick or above: tolerances on dimensions and shape. The tolerance tables themselves are copyright CEN and are not reproduced here; read the values for your thickness band from the current edition of the standard.