Square Hollow Sections · Sizing Reference

SHS Dimensions Chart

An SHS is defined by three dimensions and a basis: the outside side, the wall thickness, the length, and the standard and edition the tolerances come from. A designation like 100 × 100 × 4 mm tells you almost nothing until the fourth part is attached — because those are nominal values, and the acceptance limits around them are set by the governing standard, not by the numbers themselves. This page explains how to read and specify those dimensions, and builds a size line you can check before you send it. It does not publish a table of standard sizes here, because a size table is only trustworthy when it is reproduced from the licensed standard and its current edition.

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Price on request · availability, origin and delivery timing confirmed against the live enquiry

What actually defines an SHS

Four parts make a size line, and one of them is not a number

A square hollow section is described by its outside side, its wall thickness, its length and the standard and edition the tolerances come from. The first three are easy to copy from a drawing. The fourth is the one that decides whether the other three describe a purchasable product or an ambiguous request — because it is the standard, not the numbers, that sets what variation is acceptable and what has to be tested and documented.

Part 01

Outside side dimension

Written as a single value for SHS, e.g. 100 mm — because both sides are equal

For a square hollow section the two outside dimensions are nominally the same, which is what distinguishes it from an RHS where depth and width differ. The value is the outside face-to-face measurement, not the bore and not a mean of the two.

Fixes the envelope the section occupies on a drawing and the face the connections work to

Part 02

Wall thickness

Stated separately in the same unit system, e.g. 4 mm

Wall is stated as its own value alongside the side dimension, never assumed from it. Two sections with the same outside side can carry different walls, and the wall is what the connection design, the weld detail and the mass estimate all depend on.

Drives weld sizing, connection capacity assumptions and the mass basis

Part 03

Length

Stated with the unit system, as a stock or cut requirement

Length is a separate order input from the cross-section. A stock length and a finished cut length are different requirements, and the unit system has to match the other two values or the order line becomes ambiguous.

Separates a cross-section specification from a cut-to-length instruction

Part 04

Standard and edition

Named explicitly — the basis the tolerances and test requirements come from

This is the part most often left off, and it is the part that makes the other three mean something. The governing standard fixes the permitted variation on the outside dimension, the wall and the corner geometry, together with the ordering requirements, tests and documentation the section is supplied against.

Turns three nominal numbers into a specification a supplier can quote and an inspector can accept

Stacked square hollow section profiles with visible cut ends stored in a steel warehouse

Why this page does not print a size table

A published size table is only useful if it is reproduced from the licensed standard at the edition it applies to, with the tolerance bands and the product-form scope attached. A table copied from a secondary source, or carried over from an older edition, looks authoritative and quietly misleads — which is worse than no table at all on a page a detailer is sizing from.

So this page shows the structure of an SHS dimension, separates nominal values from tolerances, and lets you assemble and check a size line. The dimensional data itself is taken from the governing standard and the mill certificate — never from here.

See how the size-chart section is organised

Nominal values and acceptance limits

What each value on the line is, and what it is not

Most sizing mistakes are not arithmetic. They come from treating a nominal value as if it were an acceptance limit, or from assuming a geometry that the forming route actually decides. The table below separates the two for the values that appear on an SHS schedule line, and names where the real limits come from.

SHS dimensions — what each value on a schedule line is, what it is not, and where the acceptance limits come from
Value on the line	What it is	What it is not	Where the real limits come from
Outside side (e.g. 100 mm)	A nominal outside dimension — the size the section is ordered and designated by	Not a tolerance, and not a guaranteed as-supplied measurement on every length	The governing standard's dimensional tolerance for that size and wall band
Wall (e.g. 4 mm)	A nominal wall thickness stated with the section	Not a measured wall, and not interchangeable with a heavier or lighter wall of the same side	The standard's wall tolerance, which can differ by forming route and by size
Corner geometry	The outside corner radius and the resulting flat width on each face — a function of how the section is formed	Not a fixed universal value, and not safely assumed from the side dimension alone	The manufacturing route and the standard or project specification that governs it
Mass per metre	A calculated or tabulated value derived from the section's geometry and a stated density	Not a shipment weight, and not a certified value unless it comes from the mill certificate	The formula and density you use, or the standard's tabulated figure — the basis must be named
Length	An ordered length with its own tolerance regime	Not automatically the supplied length, and not a cut instruction unless it is stated as one	The standard's length tolerance, or the cut requirement on the drawing

This table carries no dimension, tolerance, radius or mass value. It describes what each field means and where its limits come from. Every dimension, tolerance and test requirement is confirmed against the governing standard, its edition and the material certificate before quotation. Price on request.

Size-line builder

Assemble the line, then check what is still missing

Enter the side, wall and length you have taken from the drawing and the basis you are working to. The builder assembles a properly formed SHS line and reports which parts are still unresolved — it does not supply a dimension, a tolerance or a mass figure of its own, because those belong to the standard you cite.

Size line

Assembled from your inputs

—

0/8

Parts unresolved

Outside side (mm or in) *

Wall thickness *

Length *

Unit system *

Governing standard *

Edition *

Grade designation

Tolerance basis

Quantity and unit basis *

Destination *

Incoterms rule

Notes

Nominal inputs kept separate from acceptance

The side, wall and length you enter are nominal values. The builder does not add a tolerance, a corner radius or a mass figure, and it does not treat a missing part as if it had been supplied. Tolerances, corner geometry and the section’s permitted variation all come from the standard and edition you cite.

Price on request. Availability, origin, certification and delivery timing are confirmed only against the live enquiry — never promised here.

Open qualified Hollow Sections RFQ

Send the size line to the commercial department; a quotation follows on your specification.

Writing it down so it survives the handover

Six habits that keep an SHS schedule unambiguous

A size schedule is read by detailers, estimators, buyers and fabricators, often weeks apart and sometimes in different countries. The habits below are what keep a line meaning the same thing to all of them — and most of them are about what gets written down rather than what gets calculated.

One unit system per line

Side, wall and length in the same units. A mixed line is the most common source of a misread schedule, and it is invisible until someone fabricates to the wrong figure.

Side and wall always together

Never write a side without its wall. The same outside dimension with a different wall is a different section, with different mass, weld behaviour and connection implications.

Name the standard and the edition

Without both, the tolerances, the grade range and the test requirements are undefined — and two suppliers can quote the same line against different bases.

Separate stock and cut lengths

A stock length and a finished cut length are different instructions. Where the member is cut, say so, and state whether the supplier or the fabricator is doing it.

Keep nominal values nominal

Do not turn a nominal dimension into a drawing tolerance unless the governing document permits it. If a tighter limit is genuinely needed, it is a project requirement to state.

Label any derived mass

If the schedule carries a mass per metre, say whether it came from a standard table or from your own calculation, and what density and geometry it assumed.

Common misreads

Three lines that look complete and are not

“SHS 100 × 100”
No wall. The most common incomplete line on a preliminary schedule — it cannot be priced, and it will be clarified before it can be ordered.
“100 × 100 × 4, 6 m”
No standard and no unit label. Whether that is a stock length or a cut length, and whose tolerance regime applies, are both still open.
“As before, same size”
A repeat instruction with no recorded basis. If the earlier order carried an edition that has since changed, the substitution is silent.

Square steel hollow sections organised on site for structural and load-bearing applications

Where the numbers actually come from

Three sources, and which one settles a dispute

A dimension on a page, a dimension on a certificate and a dimension on a delivered length are three different things. Knowing which is authoritative for which purpose is what stops a sizing reference from being mistaken for evidence.

The governing standard

Sets the nominal size range, the dimensional tolerances, the wall tolerances and the test and documentation requirements. It is the authority for what counts as acceptable — but only at the edition the project cites.

Authoritative for acceptance

The mill certificate

Records what was actually supplied for a specific consignment — chemistry, mechanical results, heat identity and the standard it was produced against. It evidences the material, not your design.

Authoritative for the consignment

A reference chart

Useful for sizing, estimating and take-off. It is a convenience reproduction, and it carries no authority in a dispute unless it is traceable to the licensed standard at the edition that applies.

Not authoritative — a working aid

This page is the third kind. It explains how the values work and how to write them, but it does not reproduce a size table and it is not evidence of what any consignment contains. For acceptance, use the standard and edition your project cites and the certificate that accompanies the material.

From a sizing need to a verified delivery

Six steps, and who closes each one

A size line begins as a detailer's decision and ends as a dimensional record on a delivered length. Each step names its owner and the item that stays open until they close it, so a nominal value is never quietly promoted into an acceptance limit on the way.

Sizing need
Detailer / engineer
In: The member's role, the design basis it sits on, and the envelope the detail has to work within.
Out: A reason for wanting a particular side and wall.
A size copied from a similar detail without a basis.
Next: Fix the envelope and the design basis.
Governing basis
Engineer / specifier
In: The standard family and the edition the project cites, and the product form it permits.
Out: The basis the tolerances and tests will come from.
A family name without an edition — tolerances left undefined.
Next: Name the standard and its edition.
Size line assembly
Detailer / estimator
In: Shape, outside side, wall, length and unit system, written consistently as one line.
Out: An unambiguous designation for the schedule.
Mixed units, or wall omitted because it seemed obvious.
Next: Write side × wall × length in one unit system.
Schedule check
Detailer / QS
In: Cross-check against the drawing, the tolerance basis and the quantity take-off.
Out: A size schedule that reconciles with the drawings.
A nominal value treated as an acceptance limit.
Next: Separate nominal values from tolerances.
Enquiry
Procurement
In: The size line with its standard, edition and tolerance basis, plus quantity, documents and destination.
Out: One enquiry a supplier can price without interpretation.
Sizes split across enquiries on different bases.
Next: Raise the enquiry on one basis.
Verification
QA / receiver
In: Material certification and dimensional records against the standard and edition ordered.
Out: Delivered section reconciled with the specification.
A certificate that does not reference the ordered edition.
Next: Check records against the ordered basis.

GCC markets & destination planning

Sizing and destination are separate questions

Getting the size line right is a technical task; landing the material is a logistics one. Confirm the consignee or importer, the port or inland delivery point, the Incoterms rule and named place, the shipment documents, and any permit or conformity step the actual goods require — then name the party responsible for each. No country card here implies a local office, a warehouse or a stock position.

United Arab Emirates

Destination and import inputs

Carry the size line, the governing standard and edition, the tolerance regime and the quantity into the UAE enquiry so the quotation and document set match the import.

United Arab Emirates hollow-section procurement

Saudi Arabia

Project specification and delivery window

Confirm the standard and edition, grade, side, wall, tolerance regime, quantity and required-on-site date so the estimate and logistics stay aligned to the governing project specification.

Saudi Arabia hollow-section procurement

Qatar

Specification and delivery inputs

State the standard and edition, grade, side, wall, delivery condition and delivery location so the Qatar quotation is fixed on a verified basis rather than an assumed one.

Qatar hollow-section procurement

Kuwait

Contractor procurement and fabrication hand-off

Link the size selection and any cutting or processing to the fabrication and inspection needs, with the delivery point and the Incoterms named place agreed against the requirement.

Kuwait hollow-section procurement

Oman

Port-oriented supply inputs

Confirm the specification, side and wall, quantities, document package, port and Incoterms rule so the Oman quotation and delivery sequencing stay aligned to the order.

Oman hollow-section procurement

Bahrain

Industrial supply inputs

Coordinate the standard edition, tolerance and inspection requirements, the document list and the delivery point to the Bahrain requirement so the section and its records arrive together.

Bahrain hollow-section procurement

Related routes

Where the sizing question ends and another begins

This page is bounded to reading and specifying SHS dimensions. Where the open question is the product family, the wider reference set, or a different structural form altogether, the routes below carry it more directly.

Steel size charts

The reference section of the knowledge centre. Start here when you need to see how sizing charts across the steel families are organised before returning to the SHS line.

Open this route

Hollow sections product range

The product family this reference serves — shapes, forms and the standards that govern them. Use it once the size line is settled and the open question is the section itself.

Open this route

Structural steel products

A comparison route, not a substitution. Where a square void is not what the detail actually needs, an open profile is a design comparison rather than a purchasing swap.

Open this route

Hollow sections for solar structures

A sizing context where repeated modules and mounting geometry drive the section choice, and where the same nominal side can be called on to do a very different job.

Open this route

Hollow sections for structural frames

Frame work is where an SHS size line most often has to answer to a connection detail rather than to a table — worth opening when the node, not the section, is the open question.

Open this route

Sizing FAQ

What a detailer or estimator asks about SHS dimensions

The questions that come up when a size line is being written or checked — how the designation is formed, why nominal values are not acceptance limits, and what has to be confirmed rather than assumed.

When should an SHS be written as one dimension and when as two?

A square hollow section is written with a single outside side value because the two faces are nominally equal — 100 × 100 × 4 mm is the same section as 100 SHS with a 4 mm wall, and the doubled form is simply the conventional way to show it on a schedule alongside rectangular sections. The moment the two face dimensions differ, it is an RHS and both values have to be stated. Writing an RHS as though it were square is one of the more common ways a schedule line becomes unbuildable.

Why can't I use these dimensions as acceptance limits?

Because everything on a designation line is nominal. The outside side, the wall and the length are the values you order by, and the permitted variation around each of them is set by the governing standard and its edition — which can differ by size band, by wall band and by forming route. A supplier is not obliged to deliver the exact nominal figure, only a section inside the tolerance the cited standard allows. If a drawing needs a tighter limit than the standard provides, that is a project requirement to state explicitly rather than an assumption to carry.

Does the corner radius matter on a square section?

It matters wherever a connection or a fit depends on the flat face. A square hollow section is formed with an outside corner radius, which means the truly flat portion of each face is narrower than the nominal side dimension. Where a plate, a cleat or a bolted fixing sits on that face, the flat width available is what constrains the detail — and it is a function of the forming route and the wall, not a fixed fraction of the side. Treat it as a question to confirm against the governing basis rather than a value to assume.

How should mass per metre be treated on a schedule?

As a derived figure with a stated basis, not as a measured or certified weight. A mass per metre comes from the section's geometry and a density, and different assumptions about corner geometry and density produce slightly different answers. It is useful for estimating and for a take-off, but the weight that matters for a shipment or a payment is the one evidenced against the order. If the project needs an authoritative figure, it comes from the standard's own table or from the mill certificate — and the schedule should say which one it used.

Can EN and ASTM square hollow sections be substituted by size?

No. A matching nominal side and wall across two standards is a coincidence of the size range, not a statement of equivalence. The two families differ in their tolerance regimes, their grade designations, their test requirements and often their corner geometry, so the same nominal line can describe two different products. A substitution is a decision for the engineer of record against the governing specification — the schedule should carry the standard and edition it was written against so the question is visible rather than assumed.

SHS size line

Send the size line with the basis attached

A square hollow section enquiry is most useful when the outside side, the wall, the length and the unit system travel with the standard, the edition and the grade the project cites. Where something is still open — an edition, a tolerance basis, a cut requirement — mark it open rather than filling it in, so the quotation is priced against a line that is genuinely complete.

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