C and MC channels are both hot-rolled steel channels with a flat web and two flanges on one side. The difference is the family of proportions: C is the standard (American Standard) channel series, and MC is the miscellaneous channel series, which covers flange widths, weights and depths the standard series does not. At the same depth, a heavy MC is wider, stiffer and stronger than any C, while a light MC can be much lighter than the lightest C. Neither letter means "better". The section that suits the job depends on what it carries and how it connects.
What "C" and "MC" mean
Both designations describe the same kind of member: a rolled channel with sloped inside flange faces, produced to the same structural steel grades and the same mill tolerances as other hot-rolled shapes.
- C (standard channel). A fixed series with depths from about 76 mm (3 in) to about 381 mm (15 in). Within each depth, the extra weight goes mostly into a thicker web, while the flange width barely changes. Canadian drawings name them by depth in millimetres and mass in kg/m, such as C200x17. Our C-channel size chart lists every standard size.
- MC (miscellaneous channel). A separate group of channels, rolled in smaller quantities, with proportions that do not fit the standard series. Some have wide, thick flanges for heavy framing. Others are deep and very light. The family also includes depths the C series does not have, up to about 457 mm (18 in).
MC sizes are usually written in imperial form (for example MC12x10.6, meaning 12 in deep and 10.6 lb/ft) even on Canadian projects, so expect to see both systems on the same set of drawings.
Side by side at the same depth
The clearest way to see the difference is to hold the depth constant. The values below are converted from the AISC Shapes Database and rounded. Use your engineer's tables or the CISC Handbook of Steel Construction for design.
203 mm (8 in) deep
| Section | Mass (kg/m) | Flange width (mm) | Web (mm) | Ix (10⁶ mm⁴) | Iy (10⁶ mm⁴) |
|---|---|---|---|---|---|
| MC8x8.5 | 12.6 | 47.5 | 4.6 | 9.7 | 0.26 |
| C200x17 (C8x11.5) | 17.1 | 57.4 | 5.6 | 13.5 | 0.55 |
| C200x28 (C8x18.75) | 27.9 | 64.3 | 12.4 | 18.3 | 0.82 |
| MC8x20 | 29.8 | 77.0 | 10.2 | 22.6 | 1.84 |
| MC8x22.8 | 33.9 | 88.9 | 10.8 | 26.6 | 2.92 |
305 mm (12 in) deep
| Section | Mass (kg/m) | Flange width (mm) | Web (mm) | Ix (10⁶ mm⁴) | Iy (10⁶ mm⁴) |
|---|---|---|---|---|---|
| MC12x10.6 | 15.8 | 38.1 | 4.8 | 23.0 | 0.16 |
| C310x31 (C12x20.7) | 30.8 | 74.7 | 7.2 | 53.7 | 1.61 |
| C310x45 (C12x30) | 44.6 | 80.5 | 13.0 | 67.4 | 2.13 |
| MC12x31 | 46.1 | 93.2 | 9.4 | 84.1 | 4.70 |
Two things stand out.
Heavy MCs put their weight in the flanges. The C310x45 and the MC12x31 weigh almost the same, but the C spends its extra steel on a thick web, which adds little stiffness. The MC spends it on wide, thick flanges, so it has about 25% more strong-axis stiffness (Ix) and more than twice the weak-axis stiffness (Iy). That makes heavy MCs useful where a channel has to resist bending in both directions or carry load sideways.
Light MCs trade strength for depth. The MC12x10.6 is as deep as a C310x31 at roughly half the weight, with a very narrow 38 mm flange. It is a good fit where depth is wanted for appearance, edge trim or to match other members, and the load is light. It is not a lighter way to get the same strength.
Where each one gets used
| Use | Common choice | Why |
|---|---|---|
| Lintels, ledgers, framing around openings | C | Stocked widely, flat back for anchors, enough strength for typical spans |
| Stair stringers | C or MC | Depth to hide tread connections; see stair stringer sizes |
| Edge trim and light fascia framing | Light MC | Depth with little weight |
| Equipment frames and heavy framing | Heavy MC | Wide flanges add weak-axis stiffness and room for bolts |
| Built-up columns and box sections | C or MC | Two channels toe to toe or back to back |
| Most beams carrying floors | Neither | A W-shape is usually more efficient; see C-channel vs I-beam |
The wider flanges of heavy MCs also leave more room for bolt holes and edge distance, which can simplify connections. On the other hand, a very narrow flange on a light MC may be too small for the bolt size the connection needs. That is a detailing check, best caught on the shop drawings rather than on site.
Availability, cost drivers and substitutions
This is where the two families differ most in practice.
- Standard C sizes are easier to find. Service centres stock the common C depths and weights. MC sections are rolled less often and in smaller runs, so some sizes may have to be sourced from further away or bought in mill quantities.
- Price is driven by weight and availability. Steel is bought largely by the kilogram, so a light MC can be economical when it is available. A section that has to be special-ordered can cost more and take longer than its weight suggests. We don't publish prices, but we can quote both options if your designer will accept either.
- Substitutions need approval. Swapping an MC for a C (or the reverse) changes the flange width, web thickness, section properties and the way connections fit. Even if the depth matches, the engineer of record has to approve it. If the drawings call for an MC that is hard to get, raise it at the quote stage, not after fabrication starts.
The grade is the same question for both. Hot-rolled channels in Canada are commonly supplied to CSA G40.21 grades or dual-certified to an ASTM grade, as explained in our guide to steel channel grades.
C channel vs channel bar
Search results for "channel" also mix in a third product: small bar-size channels, sometimes sold as "channel bar". Under the ASTM A6 definitions, shapes with every cross-section dimension below 3 in (76 mm) are bar-size shapes, rolled as merchant bar products. They look like miniature channels and are handy for light frames, trim, guards and brackets.
They are not substitutes for C or MC channels in structural framing. The smallest standard channel, C75, is about 76 mm deep, and anything smaller should be treated as a light miscellaneous component unless an engineer has designed it as part of the structure.
Telling them apart on drawings and in the shop
A few tips that save confusion:
- Read the letter carefully. "C" and "MC" on a drawing are different sections even at the same depth. An MC8x20 and a C200x28 (C8x18.75) look similar on paper but have different flange widths and properties.
- Match the units. Canadian C sizes are usually metric, and MC sizes are usually imperial. Convert with care, and if in doubt ask your designer which exact section is meant. Our guide on how to read steel beam sizes explains the naming logic.
- Check the mill certificate. If the project needs mill test certificates, they will show the section and grade supplied.
- Plan for twist. Both C and MC channels have a shear centre outside the web, so a channel loaded through its web tends to twist unless it is braced, paired or connected to resist it. The size and bracing come from the design, not from rules of thumb.
Getting C or MC channels fabricated
Whether your drawings call for a standard C or an MC, we can supply the channel cut to length and fabricated with holes, copes, clips and welded plates in our CWB certified shop, then deliver it marked and ready to install. We can prime or galvanize to suit. If a specified MC is hard to source, we'll tell you at the quote stage so your engineer can decide on an alternative before anything is cut.
Send your drawings for a quote, or browse our steel products, including channels, beams, plates and posts.
Frequently asked questions
What is MC channel steel?
MC stands for miscellaneous channel. It is a hot-rolled steel channel like a standard C, but from a separate family of sizes whose flange widths and weights fall outside the standard C series. Some MC sections are much heavier and wider than any C of the same depth, and others are very light.
Is MC channel stronger than C channel?
Not as a rule. At the same depth, the heavy MC sections are stiffer and stronger than the heaviest C, while the light MC sections are weaker than the lightest C. Compare the specific sections by their properties, not by the letter.
Can I substitute a C channel for an MC channel?
Only with the engineer's approval. A substitute changes the flange width, web thickness and section properties, which can affect strength, connections and fit with other members. Ask early if the specified MC is hard to source.
What does channel bar mean?
Channel bar usually refers to small bar-size channels, which have every cross-section dimension under 3 inches (76 mm). They are rolled as merchant bar products and used for light framing, trim and frames, not as structural C or MC sections.
