C-Channel Sizes

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

Data verified 2026-09-29 · based on ASTM A6/A6M-24

American Standard Channels (ASTM A6)

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.

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Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

Data Sources

Cross-checked against:

• Weights verified against the designation — the name states the weight per foot exactly
• Depths verified as exactly nominal, consistent with the S-shape and C-shape convention
• The area column computed from weight and checked against published areas
• Metric conversions recomputed at build time for every row

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

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.

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