An American Standard channel — a rolled section with a web and two flanges, like half an I-beam. The designation gives nominal depth and weight per foot, so C8×11.5 is 8 in deep and weighs 11.5 lb/ft.

Why does a channel twist when loaded?

Because it is not symmetric. Its shear centre lies outside the section on the side away from the web, so a load applied through the centroid creates a twisting moment as well as bending it. Load through the web, brace against twist, or use two channels back to back.

What is the difference between a C-channel and an MC-channel?

C-shapes are the American Standard channels with tapered flanges; MC-shapes are channels cut from W-shapes and have parallel flanges. MC-shapes are more efficient and take bolted connections better, but C-shapes are more widely stocked in small sizes.

How much does a C8x11.5 weigh?

11.5 lb/ft, or 17.1 kg/m. Since the weight is in the designation, a 20 ft length weighs 230 lb. Delivered weight is within rolling tolerance of the nominal figure, usually slightly under.

Where do I find channel section properties?

In the AISC Shapes Database. The nominal dimensions on this page omit the fillets, so a moment of inertia computed from them comes out 2 to 3% low, and the weak-axis properties of a channel are the ones that usually govern.

C-Channel Sizes

Nominal dimensions and weights for 28 American Standard C-channels, in inches and millimetres.

Page last changed 2026-10-19 · based on ASTM A6/A6M-24

Find a channel

American Standard Channels (ASTM A6)

Shape^[1]	Depth, d in^[1]	Flange width, bf in^[1]	Web thickness, tw in^[1]	Flange thickness, tf in^[1]	Weight lb/ft^[1]	Weight kg/m^[3]	Area (from weight) in²^[2]	Depth mm^[3]	Flange width mm^[3]
C3×4.1 #	3.000	1.410	0.170	0.273	4.1	6.10	1.205	76.2	35.8
C3×5 #	3.000	1.498	0.258	0.273	5	7.44	1.469	76.2	38.0
C3×6 #	3.000	1.596	0.356	0.273	6	8.93	1.763	76.2	40.5
C4×5.4 #	4.000	1.584	0.184	0.296	5.4	8.04	1.587	101.6	40.2
C4×7.25 #	4.000	1.721	0.321	0.296	7.25	10.79	2.130	101.6	43.7
C5×6.7 #	5.000	1.750	0.190	0.320	6.7	9.97	1.969	127.0	44.4
C5×9 #	5.000	1.885	0.325	0.320	9	13.39	2.645	127.0	47.9
C6×8.2 #	6.000	1.920	0.200	0.343	8.2	12.20	2.409	152.4	48.8
C6×10.5 #	6.000	2.034	0.314	0.343	10.5	15.63	3.085	152.4	51.7
C6×13 #	6.000	2.157	0.437	0.343	13	19.35	3.820	152.4	54.8
C7×9.8 #	7.000	2.090	0.210	0.366	9.8	14.58	2.880	177.8	53.1
C7×12.25 #	7.000	2.194	0.314	0.366	12.25	18.23	3.600	177.8	55.7
C7×14.75 #	7.000	2.299	0.419	0.366	14.75	21.95	4.334	177.8	58.4
C8×11.5 #	8.000	2.260	0.220	0.390	11.5	17.11	3.379	203.2	57.4
C8×13.75 #	8.000	2.343	0.303	0.390	13.75	20.46	4.040	203.2	59.5
C8×18.75 #	8.000	2.527	0.487	0.390	18.75	27.90	5.510	203.2	64.2
C9×13.4 #	9.000	2.433	0.233	0.413	13.4	19.94	3.937	228.6	61.8
C9×15 #	9.000	2.485	0.285	0.413	15	22.32	4.408	228.6	63.1
C9×20 #	9.000	2.648	0.448	0.413	20	29.76	5.877	228.6	67.3
C10×15.3 #	10.000	2.600	0.240	0.436	15.3	22.77	4.496	254.0	66.0
C10×20 #	10.000	2.739	0.379	0.436	20	29.76	5.877	254.0	69.6
C10×25 #	10.000	2.886	0.526	0.436	25	37.20	7.346	254.0	73.3
C10×30 #	10.000	3.033	0.673	0.436	30	44.64	8.815	254.0	77.0
C12×20.7 #	12.000	2.942	0.282	0.501	20.7	30.80	6.083	304.8	74.7
C12×25 #	12.000	3.047	0.387	0.501	25	37.20	7.346	304.8	77.4
C12×30 #	12.000	3.170	0.501	0.501	30	44.64	8.815	304.8	80.5
C15×33.9 #	15.000	3.400	0.400	0.650	33.9	50.45	9.961	381.0	86.4
C15×40 #	15.000	3.520	0.520	0.650	40	59.53	11.754	381.0	89.4

A channel is not symmetric, and that has consequences. Its shear centre lies outside the section, on the side away from the web. A load applied through the centroid — which is what a naive beam calculation assumes — therefore twists the member as well as bending it.

In practice channels used as beams are loaded through the web, braced against twist, or used back-to-back in pairs where the combined section becomes symmetric. A single channel carrying an eccentric load without restraint will twist, deflect further than calculated, and can fail by lateral-torsional buckling well below its nominal capacity.

The designation follows the same convention as other US structural shapes: nominal depth and weight per foot. The weight is exact by definition, the dimensions are nominal, and the area column is derived from the weight so that it includes the fillets the dimensions omit. Section properties come from the AISC Shapes Database.

Using Channels Properly

Channels are cheap, widely stocked and easy to work with, which makes them a common choice for purlins, girts, stair stringers, machine frames and light crane rails. Getting them to behave requires attention to the asymmetry.

Load through the web, not the centroid. The strongest and stiffest arrangement is with the web vertical and the load applied in the plane of the web. That minimises the torsional component to almost nothing and lets the channel work like a beam.

Brace against twist. Where the load is applied through the flange — a suspended load under the top flange, for instance — the member twists unless it is restrained. Sheathing, decking or discrete braces are the usual fix.

Back-to-back pairs make it symmetric. Two channels welded or bolted web to web form a symmetric box-like section with no torsional problem, and connections become far simpler. It is often cheaper than a single heavier channel despite using more steel.

Note also that a channel is weak about its minor axis if loaded from the side — a C10×15.3 has a strong-axis section modulus several times its weak-axis value. Where a channel must carry load in both directions, that ratio governs, not the strong-axis figure.

Frequently Asked Questions

What is a C-channel?: An American Standard channel — a rolled section with a web and two flanges, like half an I-beam. The designation gives nominal depth and weight per foot, so C8×11.5 is 8 in deep and weighs 11.5 lb/ft.
Why does a channel twist when loaded?: Because it is not symmetric. Its shear centre lies outside the section on the side away from the web, so a load applied through the centroid creates a twisting moment as well as bending it. Load through the web, brace against twist, or use two channels back to back.
What is the difference between a C-channel and an MC-channel?: C-shapes are the American Standard channels with tapered flanges; MC-shapes are channels cut from W-shapes and have parallel flanges. MC-shapes are more efficient and take bolted connections better, but C-shapes are more widely stocked in small sizes.
How much does a C8x11.5 weigh?: 11.5 lb/ft, or 17.1 kg/m. Since the weight is in the designation, a 20 ft length weighs 230 lb. Delivered weight is within rolling tolerance of the nominal figure, usually slightly under.
Where do I find channel section properties?: In the AISC Shapes Database. The nominal dimensions on this page omit the fillets, so a moment of inertia computed from them comes out 2 to 3% low, and the weak-axis properties of a channel are the ones that usually govern.

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#	Source	Type	Revision / method
[1]	ASTM A6/A6M — General Requirements for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling	reference	ASTM A6/A6M-24
[2]	Value computed from the standard's defining relationship	derived	Computed at build time from the defining formula and verified against every row.
[3]	Value computed from the standard's defining relationship	derived	Computed at build time from the defining formula and verified against every row.

Data Sources

Standard	Revision	What it covers on this page
ASTM A6/A6M — General Requirements for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling	ASTM A6/A6M-24	the nominal C-shape dimensions
AISC Steel Construction Manual, Shapes Database	AISC 15th edition (2017)	the section properties and the shear centre locations

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
Weight in kg/m and dimensions in mm	lb/ft × 1.48816 and inches × 25.4, exact, recomputed at build time.
Area from weight	A = weight ÷ (12 × 0.2836), which reproduces the published area to about 1%.

Weights are exact as designated and dimensions are nominal. Section properties are not given. A channel's asymmetry — shear centre outside the section — means loading position matters as much as section size, so a channel design should check torsion and lateral-torsional buckling, not just bending.

Accuracy and use. Use the source notes and recorded verification scope above to assess each value. Calculated values follow the stated derivations; compilation values may lack a confirmed original document or product condition. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Read the source notes, calculation methods and verification scope above before reusing a value. To cite this page:

Plain text

Engineering Reference. "C-Channel Sizes." https://refmanual.com/charts/c-channel-sizes/ (accessed 2026-10-19). Data from ASTM A6/A6M — General Requirements for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling, ASTM A6/A6M-24.

BibTeX

@misc{c-channel-sizes,
  title        = {C-Channel Sizes},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/c-channel-sizes/}},
  note         = {Accessed: 2026-10-19},
  source       = {ASTM A6/A6M — General Requirements for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling, ASTM A6/A6M-24}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - C-Channel Sizes
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/c-channel-sizes/
PY  - 2026
DA  - 2026-10-19
N1  - Source: ASTM A6/A6M — General Requirements for Rolled Structural Steel Bars, Plates, Shapes and Sheet Piling, ASTM A6/A6M-24
ER  -

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