Steel sheet thickness tolerances -
what they mean in practice
The thickness stated in an order is a nominal value, not a guaranteed dimension at every point of the sheet. Every product standard allows a deviation: for cold rolled sheet 1.0 mm at widths up to 1200 mm it is ±0.05 mm, for hot rolled sheet 3.0 mm at the same width ±0.20 mm, and for heavy plate 8-15 mm in class A it runs from -0.5 to +0.9 mm. These figures are not arbitrary. They follow from the physics of rolling and they decide whether delivered material complies with the contract or gives grounds for a claim.
Why a thickness tolerance exists at all
Steel strip leaves the mill in continuous motion, under pressure measured in thousands of tonnes, at varying temperature and varying uncoiling tension. The rolls deflect elastically and the material behaves unevenly across the width of the strip. The result is a natural spread of thickness, largest at the longitudinal edges and at the head and tail of the coil. The standards do not try to eliminate the phenomenon, they frame it: they define how far actual thickness may depart from nominal for the product to remain compliant.
The consequence is practical. Two sheets from the same heat, both fully compliant, may differ in thickness by a few hundredths of a millimetre. In blanking, press brake bending or spot welding that difference translates into press force, springback and process settings.
Four standards, four fields of application
The first step in assessing a delivery is to establish which standard applies to the product. The split is unambiguous and depends on the production route and on whether the product is coated.
| Standard | Products covered | Dimensions covered |
|---|---|---|
| EN 10051 | continuously hot rolled strip and plate or sheet cut from wide strip | thickness up to 25 mm, rolled width 600-2200 mm |
| EN 10029 | hot rolled heavy plate | thickness 3-400 mm, width from 600 mm |
| EN 10131 | cold rolled uncoated and electrolytically zinc coated flat products | thickness 0.35-3.00 mm, width from 600 mm |
| EN 10143 | continuously hot dip coated products, including zinc, zinc-iron, zinc-aluminium, aluminium-zinc and aluminium-silicon coatings | thickness 0.20-6.50 mm |
The distinction matters for a second reason: the letters A, B, C and D appear in two different meanings. In EN 10051 they denote steel categories by specified minimum yield strength, category A covering material up to 300 MPa and the following categories stronger material, with the tolerance widening as the category rises, because dimension is harder to hold when rolling stronger steel. In EN 10029 the same letters denote tolerance classes, that is how the deviation is distributed between the plus and the minus side. Confusing the two systems leads to disputes in which both parties invoke class A while meaning different things. The symbols of the material itself are covered in the article on steel sheet grade designations.
Values that can be checked in a delivery
The summary below covers the thicknesses most common in industry, at widths up to 1200 mm. For hot rolled product these are category A values, for cold rolled and hot dip coated product the values for material with a yield strength below 260 MPa.
| Nominal thickness | Hot rolled (EN 10051) | Cold rolled (EN 10131) | Hot dip coated (EN 10143) |
|---|---|---|---|
| 1.0 mm | ±0.17 mm | ±0.05 mm | ±0.06 mm |
| 2.0 mm | ±0.17 mm | ±0.10 mm | ±0.12 mm |
| 3.0 mm | ±0.20 mm | ±0.15 mm | ±0.17 mm |
| 6.0 mm | ±0.26 mm | outside the scope | ±0.22 mm |
| 10.0 mm | ±0.32 mm | outside the scope | outside the scope |
In EN 10051 all thicknesses below 2.00 mm fall into a single table row, hence the same value for 1.0 and 2.0 mm.
Two conclusions follow at once. First, at the same nominal thickness the band for cold rolled product is clearly narrower than for hot rolled: by two fifths at 2.0 mm and by a quarter at 3.0 mm. Second, the band widens with thickness, but more slowly than the thickness itself, so in percentage terms dimension is hardest to hold on the thinnest material.
For higher strength material the bands are wider. At a yield strength of 340-420 MPa the tolerance for cold rolled sheet 1.0 mm rises to ±0.07 mm and for 3.0 mm to ±0.20 mm. In hot dip coated products with a yield strength of 420-900 MPa the tolerance for 2.0 mm reaches ±0.18 mm. Higher strength therefore carries a price in lower dimensional repeatability.
Special tolerances
EN 10131 and EN 10143 provide special, narrowed tolerances alongside the normal ones, designated by the letter S. For cold rolled sheet 0.80-1.00 mm the normal tolerance is ±0.05 mm and the special one ±0.035 mm. For coated product 0.60-0.80 mm the values are ±0.05 mm and ±0.040 mm respectively. For heavier coating masses, Z450 and Z600, 0.01 mm is added to the table value, because the coating itself is part of the measured thickness.
Special tolerances are ordered where the downstream process is sensitive to dimensional variation: in deep drawing, in automated resistance welding, on lines running without resetting between batches. A narrowed tolerance has to be stated in the order. Its absence means delivery to normal tolerances and is not a defect.
Tolerance classes for heavy plate
EN 10029 works differently. Rather than narrowing the band, the standard shifts it relative to the nominal dimension and leaves the choice to the purchaser.
| Class | Distribution of the deviation | Example for 5-8 mm |
|---|---|---|
| A | narrowest band, minus deviation growing with thickness | -0.4 to +0.8 mm |
| B | minus side fixed, independent of thickness | -0.3 to +0.9 mm |
| C | zero lower limit, the whole tolerance on the plus side | 0 to +1.2 mm |
| D | symmetrical distribution | -0.6 to +0.6 mm |
Class C matters in structures where nominal thickness is also the design thickness. It allows no undersize, so every plate is guaranteed at least the nominal thickness, at the cost of a larger mass allowance. Class D spreads the deviation evenly and loads the plus side least, while class A gives the narrowest overall band. For 8-15 mm the corresponding values are -0.5 to +0.9 mm in class A and -0.7 to +0.7 mm in class D.
Where and how thickness is measured
Differences in assessing a delivery often arise not from the material but from the way it is measured. The standards are precise on this point.
Under EN 10051 thickness is measured at a point at least 40 mm from the edge for mill edge products and at least 25 mm for trimmed or slit edges. EN 10131 and EN 10143 require a point more than 40 mm from the edge, and for products narrower than 80 mm the measurement is taken on the centre line. EN 10029 requires a point more than 25 mm from the transverse and longitudinal edges, excluding locally ground areas.
A measurement taken at the very edge of a sheet will always give a less favourable result and is not a measurement to the standard. It is the first thing a supplier checks when a dimensional non-conformity is reported.
Thickness tolerance and shape tolerances
Thickness, flatness, edge camber and squareness are covered in separate clauses of each of these standards and measured independently. Thickness describes the dimension at a given point. Flatness and camber describe the geometry of the whole sheet or strip: departure from a plane and departure of the edge from a straight line. For cold rolled sheet, edge camber should not exceed 5 mm over a length of 2 m and out of squareness 1 percent of sheet width.
The distinction matters in practice, because a sheet can sit in the middle of the thickness band and still be unusable for automatic feeding because of camber. The reverse holds as well: material at the lower thickness limit may run on the line without any trouble. These relationships are covered more widely in the article on surface defects of second-grade steel sheet.
Dimension and delivered mass
Thickness bears directly on mass, and mass on settlement. Sheet 2.0 mm delivered at the lower EN 10051 limit, that is 1.83 mm, yields about 9 percent more area per tonne than the nominal thickness, and against material at the upper limit of 2.17 mm the difference reaches about 19 percent. Where the number of blanks per tonne counts, this feeds straight into unit cost. Where load capacity or stiffness counts, only the lower limit matters.
This is also why material with an actual thickness close to the lower limit is sought by some buyers and rejected by others. The mere fact that sheet is thinner than nominal is not a defect as long as it stays within the tolerance of the relevant standard.
Dimension and material classification
Material sold outside the primary distribution channel, known on the market as non-prime or second grade, has no separate definition in the standards. European producers run its sale as a separate channel, describing it as steel that is often fully compliant with the European standards. Trade publications point to surface appearance and to commercial decisions taken by mills in periods of weak demand as the dominant downgrading criteria, rather than an automatic breach of dimensional tolerance.
For the buyer this means one thing: when purchasing from that channel, the key is to establish what departs from full compliance and what stays within the standard. A batch downgraded because of surface appearance or stock age carries the same dimensional tolerances as prime material. The characteristics of such material are set out in the article on second-grade steel sheet.
Stating the dimension in an order
An order that defines the dimension unambiguously states the product standard, the nominal thickness, the width, the steel category or tolerance class where the standard provides for them, and any requirement for special tolerances. For heavy plate it adds class A, B, C or D. Such wording closes the room for interpretation on both sides and reduces any claim procedure to a straightforward measurement.
Available steel grades, coating types and formats of coils, slit strip and sheets are presented in the HEN-STOL steel sheet offer, with separate pages for galvanized steel sheet, cold-rolled steel sheet and hot-rolled steel sheet.
See how we can help
Send us the specification of the material you currently use: grade, thickness, width, required tolerance, coating type, preferred delivery form and batch size. We will verify availability and present the best terms we can offer. If the dimensional requirements turn out to be set above what the process actually needs, we will point to material matching the real requirements of the product.
Frequently asked questions
Is sheet thinner than nominal defective?
No, as long as it stays within the tolerance of the relevant product standard. For cold rolled sheet 1.0 mm at widths up to 1200 mm the lower limit is 0.95 mm and such material fully complies with the order. A dimensional defect starts only beyond the band defined in the standard.
Which standard applies to galvanised sheet?
Dimensional tolerances of continuously hot dip coated products are set by EN 10143, covering thicknesses from 0.20 to 6.50 mm. Technical delivery conditions, grades and coating masses are governed separately by EN 10346. For Z450 and Z600 coatings the table tolerance increases by 0.01 mm.
Do special tolerances have to be ordered separately?
Yes. EN 10131 and EN 10143 provide them as an option designated by the letter S. Without explicit wording in the order, delivery is made to normal tolerances, and the difference can be substantial: for cold rolled sheet 0.80-1.00 mm it is ±0.05 mm against ±0.035 mm.
Why does a measurement at the edge give a different result?
The largest thickness deviations occur at the longitudinal edges of the strip, which is why the standards exclude the edge zone from measurement. EN 10051 sets 40 mm for mill edges and 25 mm for trimmed edges, EN 10131 and EN 10143 more than 40 mm, and EN 10029 more than 25 mm from the edge.
Does thickness tolerance affect the mass of an order?
Yes. Theoretical mass is calculated from nominal thickness, while actual mass follows the real dimension. For sheet 2.0 mm within the EN 10051 tolerance, the extreme thicknesses of 1.83 and 2.17 mm differ by about 19 percent in the area obtained from a tonne of material.
Does second-grade material have different tolerances?
The standards define no separate tolerances for this category, because the category itself is not defined in them. What matters is the feature that excluded the batch from the primary sales channel. Material downgraded on visual grounds keeps the dimensions required by the product standard.
Sources
- EN 10051, Continuously hot-rolled strip and plate/sheet cut from wide strip of non-alloy and alloy steels, tolerances on dimensions and shape
- EN 10029, Hot-rolled steel plates 3 mm thick or above, tolerances on dimensions and shape
- EN 10131, Cold rolled uncoated and electrolytically zinc or zinc-nickel coated flat products, tolerances on dimensions and shape
- EN 10143, Continuously hot-dip coated steel sheet and strip, tolerances on dimensions and shape
- ArcelorMittal Europe Flat Products, Tolerance and conversion tables
- SSAB, Dimensional and shape tolerances, cold rolled steel sheets and coils
- ArcelorMittal Europe Flat Products, Non-prime sales
- Metal Center News, Secondary report, K. Zajac-Frazee, July 2026