Standards guide · Steel caps

Steel caps: dimensions to EN 10253-2

Butt-welding caps in steel are standardised in EN 10253-2. This page carries the figures: pick the outside diameter and the wall thickness series, and the dimension finder shows the dimensioned drawing, the dimension table and the limit deviations for exactly that size. A cap closes a pipe end with a cylindrical straight flange, a knuckle and a crown – what separates it from a dished end, and how type A differs from type B, is explained on the caps and dished ends page.

Standard: EN 10253-2:2026-07
Material: non-alloy and alloy steel
Design: cap
Dimension: K

Dimension finder: dimensioned drawing for one specific size

Select outside diameter and wall thickness series – the drawing and the dimension table then show exactly that size, with the figures in the drawing itself instead of only the dimension letters. What separates type A from type B, is on the basics page. The dimension tables for the sizes listed here are further down this page.

Design variant

Typ A (body like the pipe) Typ B (cap body reinforced)

Outside diameter

Wall thickness series

EN 10253-2 covers the greyed-out sizes. Our dimension overview lists them as order dimensions – see the table “Further deliverable dimensions” below.

Steel cap · 114.3 × 3.6 mm

Cap in steel, 114.3 × 3.6 mm: section in the axial plane with the overall height K, below it the view onto the butt weld end. The contour follows Figure 8 of the standard – cylindrical straight flange, knuckle with R2, crown with R1. The standard names both radii only in a legend as approximately equal, not as a dimension.

Technical basis: DIN EN 10253-2:2026-07. Zickwolff has prepared this presentation for practical use, with our own structure, our own designations and a statement of what kind of value each figure is. The original standard governs normative requirements.

Dimensions of the cap in steel, 114.3 × 3.6 mm
Property	Value	Type of information
basic data
Wall thickness series	Series 2	standard dimension
Availability	from stock or procured	trade information
nominal size	DN 100	assignment
connecting dimensions The dimensions at the welding ends that govern the joint with the pipe that follows.
outside diameter D	114.3 mm	standard dimension
wall thickness T	3.6 mm	standard dimension
inside diameter	107.1 mm	calculated
installation dimensions The dimensions that determine the installation space.
overall height K	64 mm	standard dimension
type A or type B Both designs in the standard have identical connecting dimensions. They differ in exactly these two values – type A carries less internal pressure than the straight pipe, type B is reinforced at the fitting body so that it matches it.
pressure factor (type A only) X	100 %	standard value
wall thickness at the cap body (type B only) T_c	3.6 mm	standard value (not binding)

Without an entry in the “Type of information” column: standard dimension. A dimension that EN 10253-2 specifies for this size.

Where exactly it is measured

outside diameter D: measured across the edge at the welding end
wall thickness T: at the welding end – on the dished part the wall may be thinner
inside diameter: ID = D − 2T
overall height K: from the edge of the welding end to the crown
pressure factor (type A only) X: ratio of the pressure resistance of the fitting to that of a pipe of the same wall thickness
wall thickness at the cap body (type B only) T_c: on the dished part – T still applies at the welding end

Tolerances (limit deviations): what range the standard permits

For each dimension the range that EN 10253-2 permits is given – minimum and maximum instead of the deviation that would first have to be worked out. In the drawing this is shortened to tolerance – the word everyone uses in practice. In technical terms the two values given are the limit dimensions of the dimension, their distance is the tolerance and the deviations from the nominal size are the limit deviations. The basis is clause 11.2 with Table 12 and Table 13, and clause 11.3 – where the standard specifies nothing, that is stated.

These dimensions have two limit deviations – which one applies depends on the specific part

For the following dimensions the standard specifies two limit deviations. Which one applies does not depend on the nominal size but on the specific part. Both cases are therefore written out.

This answer determines: out-of-roundness O_v.

out-of-roundness O_v – calculated as 100 · (Dmax − Dmin)/D, largest and smallest outside diameter in the same cross-section at the welding end

Where is the out-of-roundness measured? (the standard allows more out-of-roundness on the body of the fitting than at the weld ends. The weld ends are the two straight, flat end faces at which the part is welded into the line – the body is everything in between, on a elbow the curved section, which inevitably becomes somewhat oval in bending. What is measured, in one and the same cross-section, is the largest outside diameter minus the smallest)

at the weld ends out-of-roundness Up to D 273.0 no separate limit is specified – but Dmax and Dmin must each lie within the limit deviation of the diameter, and that limits the difference by itself.
I don't know both cases remain

What the standard specifies beyond the dimensions in the drawing

The following requirements are not tied to any dimension in the drawing. They are set out here in the structure of the standard, under its own headings. The label on each line says what kind of information it is – a dimension from the standard, a statement of the standard, an acceptance criterion on the finished part, or a manufacturing requirement.

out-of-roundness

out-of-roundness O_v standard value	Up to D 273.0 no separate limit is specified – but Dmax and Dmin must each lie within the limit deviation of the diameter, and that limits the difference by itself.

Every dimension has its reason – whoever knows why they measure, measures better.

limit deviations for the wall thickness

wall thickness at the fitting body statement of the standard	At the fitting body no upper limit deviation of the wall thickness is defined (option 12: as ordered).

limit deviations for selected dimensions and form tolerance

fitting geometry (squareness and alignment deviation) standard value	at most 1.14 mm (1 % of D, at least 1 mm)

The standard checks all limit deviations for the fitting geometry in the same position of the fitting (figure 9).

end preparation

bevel angle design rule	limits 30° to 35°
root face design rule	limit dimensions 0.8 to 2.4 mm
rework: outside bevel angle design rule	at most 30°
rework: inside bevel angle design rule	at most 18°
burrs at the ends design rule	The ends of the fitting shall be free from dangerous burrs.

Sources of the limit deviations (11 entries)

out-of-roundness (at the weld ends) – 11.2.2
wall thickness at the fitting body – 11.2.3 NOTE
fitting geometry (squareness and alignment deviation) – 11.2.4 and Figure 9 (there: X)
bevel angle – 11.3 and Figure 11
root face – 11.3 and Figure 11 (the root face is called C there)
rework: outside bevel angle – 11.3
rework: inside bevel angle – 11.3
burrs at the ends – 11.3
outside diameter – 11.2.1.1
wall thickness – Table 12
overall height – Table 13

This information does not replace the standard itself. Only the limit deviations for the size selected here are reproduced. In full – for all dimensions and fittings of the standard – they are given in DIN EN 10253-2:2026-07, clause 11.2 with Table 12 and Table 13, and clause 11.3. Where to obtain it: DIN Media.

Why limit deviations exist at all and how to read them is explained on a page of its own: Tolerances and limit deviations.

Dimensions are nominal dimensions to EN 10253-2 and do not replace the data sheet of the actual item. No statement about pressure or temperature suitability and no statement about the material. K is the overall height from the edge of the butt weld end to the crown. The standard names the two radii only in a legend as approximately equal and does not dimension them. Direct link to this size

The standard names dimensions. What is listed here is deliverable – from stock or procured; how quickly a size is available we clarify on request.

How to measure correctly

A cap is identified by three measurements: outside diameter D and wall thickness T at the welding end, and the overall height K from the edge of the welding end to the crown. On the dished part the wall may be thinner than at the welding end – so always measure T at the end.

outside diameter D: measured across the edge at the welding end
wall thickness T: at the welding end – on the dished part the wall may be thinner
overall height K: from the edge of the welding end to the crown

A measured value rarely matches the table exactly. The dimension finder on this page shows the limit deviations of EN 10253-2 for every size.

Type A and type B

Worth knowingPurchasing explains

Type A and type B – what the difference really means

A fitting is a formed piece of pipe – bent, expanded, necked-in or drawn. In forming, material migrates, and in some places the wall becomes thinner or the shape carries the pressure less well than a straight pipe. That is exactly where the distinction starts.

Type A is the fitting with pipe wall thickness. At the welding ends and at the body it has the same wall thickness as the pipe it goes with. The standard states expressly that its internal pressure resistance is lower than that of a pipe of the same diameter, the same wall thickness and the same material. By how much lower is stated by the pressure factor – a percentage that the standard lists for every size in tables of its own. 80 % means: the part carries four fifths of what the pipe carries.

Type B is the fitting that does not weaken the line. It has an increased wall thickness at the body and thereby achieves the same pressure resistance as the pipe. How much wall is needed for that, the standard calculates in an annex of its own.

What this means in practice. With type B you simply calculate the line with the pipe wall thickness – the fitting is never the weakest point. With type A you have to know the pressure factor and either reduce the permissible pressure or choose a thicker wall from the outset. That is why the type belongs in the enquiry and not in the follow-up question – it is part of the designation, not an extra.

And it is not a question of material. Type A and type B exist in steel as in stainless steel – they differ in geometry and in the verification, not in the alloy.

From the standard: DIN EN 10253-2:2026-07, clauses 7.1 to 7.3 (standard page 18) and DIN EN 10253-4:2025-10, clause 7 – both read from the page image. Annex B (calculation), Annex C (pressure factors type A), Annex D (wall thicknesses type B).

Worth knowingThe inspection body explains

Why type B changes hardly anything for a cap

For elbows and tees the difference between the types is tangible: there, type B adds a noticeable amount of wall. For a cap, hardly at all – and there is a good reason for that.

The pressure factor of a type A cap averages 99.8 % across all sizes of our dimension overview and never drops below 94 %. For comparison: an elbow averages 77 %, a tee 45 %. So a cap is, even as type A, practically as strong as the pipe it is welded to. The dished shape carries the internal pressure almost as well as a straight cylinder. On a tee, by contrast, the hole for the branch takes material away from the pressure-retaining wall, and type B has to bring that back.

In numbers it looks like this: of the sizes for which the standard states a type B wall thickness, in 93 cases it is exactly the pipe wall thickness – there, type B does not change a tenth of a millimetre. Only in 7 sizes is it larger, namely by 0.1 to 0.5 mm at the large diameters from 610 to 1219 mm. For a further 61 sizes the standard states no value at all.

So what is type B for on a cap? Because with it you are not buying a wall thickness but a commitment – the strength is verified according to the annex of the standard, and the pipe class may be calculated with the pipe wall thickness without an exception rule. At the large diameters you additionally really do get some wall. So whoever specifies type B throughout does nothing wrong with the cap – they should just know that for caps it usually means the same part.

Own derivation – not a statement of the standard: Counted over DIN EN 10253-2:2026-07, Annex C Table C.5 (pressure factors type A) and Annex D Table D.7 (wall thicknesses type B), both captured from the page image. The percentages and counts are our own count, not text of the standard.

Type A and type B: the pressure factor

A dished cap carries the internal pressure differently from the straight pipe. The standard describes this with two versions:

Version

Type A – reduced pressure factor

Wall thickness at the cap body as at the welding end. How much internal pressure the cap carries compared with the straight pipe is stated by the pressure factor X in per cent – Table C.5, in the tables below for every size and series.

Version

Type B – full pressure resistance (standard: “for use at full service pressure”)

Increased wall thickness at the cap body, designed for the same internal pressure as the straight pipe. The wall thickness T_c is not specified – smaller wall thicknesses are permissible if they are calculated according to Annex B.

We have recalculated each of the 100 cells of Table C.5 via the equations of Annex B and matched them completely.

The table of Annex D calculates with R₂ = 0.15 × D and R₁ = 0.8 × D. Whoever orders a cap with a smaller knuckle radius or a larger dishing radius (in the standard: inside spherical radius) must have the wall thickness at the cap body calculated according to Annex B – the table values then do not apply.

Installation dimension

The overall height K – and why there can be two of them

The cap has exactly one overall dimension: K, the overall height from the edge of the welding end to the crown. For most sizes the standard names a single value for it.

From ⌀ 711 mm no longer. There, Table A.4 carries two overall heights per outside diameter, and which one applies is decided by the wall thickness: at ⌀ 914, for example, 267 mm up to and including 10 mm wall thickness and 370 mm above that. Whoever reads only the diameter row picks the wrong height for every second large cap. In the dimension tables below there is therefore one row per size and wall thickness series – the height next to it is always the one that belongs to this wall thickness.

The permissible deviations of K are graded by diameter: ± 4 mm up to ⌀ 114.3, above that ± 7 mm and from ⌀ 762 ± 10 mm. The drawing above shows them in tolerance mode as a second line at the dimension.

The standard dimensions nothing more on the dished shape. The straight flange, the knuckle and the crown are described by the two radii of the figure key, and those are “approximately equal” – the drawing says so in its footer.

Tolerances and testing

Worth knowingThe site crew explains

Whether you get a bevel is decided by the wall thickness – and the limit is 3.2 mm

The standard regulates the ends in three steps. Below 3.2 mm wall thickness the manufacturer may leave the end square – for steel a slight bevel is also permitted, for stainless steel the standard names only the square cut. From 3.2 mm to 20.0 mm the end must be bevelled, and precisely so: angle 30 degrees with +5 degrees allowance upwards and nothing downwards, root face 1.6 mm ± 0.8 mm. Above 20 mm the standard specifies nothing further – then the joint preparation is to be agreed.

The number to remember is 3.2. It is not a rounded 3 but a limit set by the standard, and it decides whether rework is needed on site. Whoever orders a wall thickness just below it may receive a square end and has to prepare the joint on site.

Rework is permitted, but limited: if the welding ends have to be machined, the wall thickness may be reduced by bevelling – outside at most 30 degrees, inside at most 18 degrees. And the ends must be free of dangerous burrs. Both are found in the same passage as the bevel.

From the standard: DIN EN 10253-2:2026-07, 11.3 with Figure 11 (standard page 45) · DIN EN 10253-4:2025-10, 11.3 with Figure 17 (standard page 40) · both read from the page image

Limit deviations and out-of-roundness

Tolerance rules — they apply to all sizes
D	± 1 %, at least ± 0.5 mm, at most ± 5 mm
K	± 4 mm for D up to 114.3 ± 7 mm for D above 114.3 up to 762 ± 10 mm for D above 762
T	+20 % / −12.5 % for D up to 610 plus 5 rules that depend on a question to be answered (e.g. the method of manufacture) — they are in the tolerance block of the dimension finder

The drawing above carries the complete tolerance block – here the points that are particular to caps:

One welding end, one graduation. Diameter and wall thickness limit deviations apply at the welding end with D and T. Unlike the reducer or tee, there is no second end with values of its own.
Out-of-roundness at the welding end. Up to ⌀ 273 it is included in the diameter limit deviation, above that 2 % applies, above ⌀ 610 then 1 %. There is no out-of-roundness limit at the fitting body: according to clause 11.2.2 the 4 % applies only to elbows and 180° elbows.
No inside-diameter condition. The rule according to which the inside diameter must at all points exceed 80 % of the value at the welding ends is expressly excepted by clause 11.2.1.2 for caps and dished ends – a component that closes the pipe has no flow. On the pages on elbows, tees and reducers it is therefore stated, here it is not.
No corrugation. The limit values for corrugation (h_m, LE) apply to elbows, tees and reducers – not to this component.

Above ⌀ 610 mm the wall thickness limit deviations depend on whether the fitting is seamless or welded. Below that, the distinction makes no difference to the dimensions.

Limits of this page

Worth knowingThe inspection body explains

At the welding end, the fitting is measured with the same yardstick as the pipe

The limit deviation for the outside diameter in EN 10253 reads “±1 % or ±0.5 mm, whichever is greater” – and the tube standards of the EN 10216 series carry the same sentence, word for word. Out-of-roundness coincides too: 2 % here as there. That is no accident but intent: the welding end is where the weld is made, and what meets there has to fit together.

Both families of standards therefore distinguish the same two places – the body and the ends. API 5L lists the columns “pipe body” and “pipe ends” side by side, EN 10208 states expressly that the limit deviations do not apply to the pipe ends because they are regulated separately there. And the fitting standard, conversely, expressly measures at the welding ends.

The wall thickness coincides too, where it counts. The lower limit deviation is −12.5 % for both – and that is the one that matters, because it decides the pressure resistance. Upwards, the fitting allows more: +20 % instead of +12.5 % for the pipe. The reason is the forming – material that piles up during upsetting does no harm. Above ⌀ 219.1 the pipe additionally grades its lower limit deviation by the ratio of wall thickness to diameter, the fitting does not.

Two differences remain, and both have a reason. The fitting caps its diameter limit deviation at ±5 mm – from ⌀ 500 it is therefore toleranced more tightly than the pipe. And above ⌀ 610 it demands 1 % out-of-roundness where the pipe allows 1.5 %. The fitting is the formed part – it has to adapt to the pipe, not the other way round.

From the standard: DIN EN 10253-2:2026-07, 11.2.1.1 and 11.2.2 · EN 10216, EN 10208, EN 10217 and API 5L as given in Tabellenbuch Rohrleitungsbau, section 2.1.3

What this page does not say

No weight. Neither the standard nor our catalogue lists weights for caps. We do not calculate one: a calculated weight would look on this page exactly like a substantiated one.
Not every size has a type B wall thickness. Where the column T_c shows a dash, the dimensions of the cap lie outside the scope of the calculation method of Annex B – so says clause D.5. The footnote under the table says so again at every point.
No statement on availability. The standard names sizes – our stock is another matter. What is available is shown in the shop.

We spell this out instead of silently smoothing it over: a gap that can be seen is something different from a guessed number.

Read on

Dimension tables for Caps in steel: 28 rows

Zickwolff dimension overview (standard reference EN 10253-2). If you need a dimensioned drawing for one of these sizes, the dimension finder at the top of this page has it.

Caps outside the preferred series Further deliverable dimensions

Caps – sizes and series

One row per size and wall thickness series. T is the wall thickness at the butt weld end, K the overall height.

Doutside diameter in mm	DNnominal size	Serieswall thickness series	Twall thickness in mm	Koverall height in mm	Xpressure factor (type A only) in %	T_cwall thickness at the cap body (type B only) in mm
21.3	15	2	2	25	–¹	–²
21.3	15	4	3.2	25	–¹	–²
26.9	20	2	2.3	25	–¹	–²
26.9	20	4	3.2	25	–¹	–²

Show full table · more than 20 rows

Caps in steel to DIN EN 10253-2:2026-07, from stock or procured – 28 rows, all dimensions in millimetres.
Doutside diameter in mm	DNnominal size	Serieswall thickness series	Twall thickness in mm	Koverall height in mm	Xpressure factor (type A only) in %	T_cwall thickness at the cap body (type B only) in mm
21.3	15	2	2	25	–¹	–²
21.3	15	4	3.2	25	–¹	–²
26.9	20	2	2.3	25	–¹	–²
26.9	20	4	3.2	25	–¹	–²
33.7	25	2	2.6	38	100	2.6
33.7	25	4	4	38	–¹	–²
42.4	32	3	3.6	38	–¹	–²
42.4	32	4	4	38	–¹	–²
48.3	40	2	2.6	38	100	2.6
48.3	40	4	4	38	–¹	–²
57	–	2	2.9	38	–¹	–²
60.3	50	2	2.9	38	100	2.9
60.3	50	4	4	38	100	4
76.1	65	2	2.9	38	100	2.9
88.9	80	2	3.2	51	100	3.2
114.3	100	2	3.6	64	100	3.6
114.3	100	3	4.5	64	100	4.5
133	–	2	4	70	–¹	–²
139.7	125	2	4	76	100	4
159	–	2	4.5	84	–¹	–²
168.3	150	2	4.5	89	100	4.5
219.1	200	2	6.3	102	100	6.3
273	250	2	6.3	127	100	6.3
273	250	4	10	127	100	10
323.9	300	2	7.1	152	100	7.1
355.6	350	2	8	165	100	8
406.4	400	2	8.8	178	100	8.8
508	500	3	11	229	100	11

standard dimension: D, T, K · standard value: X · standard value (not binding): Tc · assignment: DN

¹ For this size the standard gives no pressure factor – this combination of diameter and wall thickness is not in the table. (11 cells)

² For this size the standard gives no wall thickness at the cap body: the dimensions of the cap lie outside the scope of the calculation method in annex B. (11 cells)

Dimensions outside the preferred series

EN 10253-2 pairs diameter and wall thickness through a series number. The sizes below we carry with a wall thickness that is in no series for that size – or with two wall thicknesses that are each in the standard, but not in the same series. The dimensions are established in the same way as in the grid above. Where the standard gives its values through the series number, the cell stays empty.

Dimensions outside the preferred series to EN 10253-2, from stock or procured – 3 rows, all dimensions in millimetres.
Doutside diameter in mm	nominal size in DN	Twall thickness in mm	inside diameter in mm	Koverall height in mm
76.1	65	5	66.1	38
88.9	80	4.5	79.9	51
108	–	5	98	60

Where a dash stands, EN 10253-2 gives the value through the series number – and this row has no series number. This affects the guide mass from the catalogue table and, on the pipe end closures, the pressure factor and the type B wall thickness from the annexes. Nothing is calculated in their place.

Further deliverable dimensions (32)

Show full table · more than 30 rows

Further deliverable dimensions – 32 rows, from stock or procured, all dimensions in millimetres.
Doutside diameter in mm	Twall thickness in mm
101.6	3.6
101.6	5.6
101.6	8
457	10
457	11
457	12.5
610	10
610	12.5
610	17.5
610	30
813	8
813	8
813	12.5
813	12.5
914	10
914	10
914	12.5
914	12.5
914	25
914	25
1016	10
1016	10
1016	12.5
1016	12.5
1118	10
1118	10
1118	12.5
1118	12.5
1219	10
1219	10
1219	12.5
1219	12.5

Order dimensions and values calculated by us; deliverable from stock or procured, availability on request. Limit deviations and figures from the standard: see the main table and the standard itself.

The dimensions given are nominal dimensions. The text of the standard prevails. The German edition DIN EN 10253-2:2026-07 reproduces the European version EN 10253-2:2021+A1:2025.

What has changed since the earlier edition

For the cap, the comparison covers the editions from DIN EN 10253-2:2008-09. Not yet recorded: DIN 2617.

DIN EN 10253-2:2008-09 → DIN EN 10253-2:2021-11

value
The cap height K has changed for two sizes.

Examples: ⌀ 33.7: 25 to 38 · ⌀ 101.6: 64 to 60

editions 2008-09 and 2021-11 · Table 16 and Table A.4
value
The cap table has added nine diameters that it did not carry before.

Examples: ⌀ 38 · ⌀ 108 · ⌀ 193.7

editions 2008-09 and 2021-11 · Table 16 against Table A.4
value
One diameter of the cap table has changed by 2 mm - the associated height K stayed the same.

Examples: ⌀ 1166 became ⌀ 1168

editions 2008-09 and 2021-11 · Table 16 against Table A.4
system
The cap table no longer carries a DN column - it names only the outside diameter D.

editions 2008-09 and 2021-11 · Table 16 (DN, D, k) against Table A.4 (D, K)

DIN EN 10253-2:2008-09 → DIN EN 10253-2:2026-07

unchanged
The standard carries the wall thicknesses of type B caps in both editions - in 2008 as Table C.7, today as Table D.7, with matching sample values.

Examples: ⌀ 21.3 series 2: T 2 · ⌀ 610 series 5: T 25 / Tc 25.0

editions 2008-09 and 2026-07 · Table C.7 (edition 2008) against Table D.7 (edition 2026)

These entries say what the standard has changed. They say nothing about material, pressure rating, scope of testing or the condition of an installed part — and nothing about whether an existing part can continue to be used. That assessment remains with the specific plant.

Caps by dimension – ask our warehouse

You know the size? Send us the outside diameter with its wall thickness, together with the material and the inspection document required. Our export team answers in English, with price, availability and certificate.

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How this data is compiled. This page does not reproduce a standard. It shows the dimensions you need for an enquiry, an order and installation – for sizes we supply, checked against documents from manufacturing works and suppliers and against our own range. Each value states what kind of value it is: specified by the standard, calculated by us or customary in the trade. The currently valid standard is binding. It is available from DIN Media or from your national standards body. How we select our sources and keep them up to date: About this knowledge.

Technical basis: DIN EN 10253-2:2026-07 (butt-welding fittings of non-alloy and alloy steel), EN 10204. All information without guarantee – the current standard texts and the manufacturers’ technical data sheets always prevail.