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The channel's overall depth, measured across the web between the outside faces of the flanges.
Outside to outside across the back of the channel, which is the dimension a channel is designated by. Measure on the web's outside face, not between the flange tips — a channel's flanges taper on the older rolled sections, so the tip and the root are different thicknesses and neither is the depth.
The width of each flange leg, measured from the web.
From the outside face of the web to the flange tip. On a parallel-flange channel this is a straight measurement; on a tapered-flange section the flange has a slope and the width is still taken to the tip. Both flanges are the same on a rolled channel — if they are not, the section is a fabricated one and is not what this calculation weighs.
The thickness of each flange.
The flange thickness, taken at the point the shape table quotes — mid-flange on a tapered section, which is thicker at the root and thinner at the tip. Using the tip thickness on an old tapered channel makes the section light by a noticeable margin, and the flanges are where most of a channel's steel is.
The thickness of the web connecting the two flanges.
The flat part between the flanges, measured clear of the root radii where the web thickens into the flange. The web is thinner than the flanges on almost every rolled channel and contributes less weight than its area suggests, because the fillets at the roots add steel this calculation does not count — expect a nominal-dimension weight to sit a per cent or two under the table.
Weight per unit length
12.8 lb/ft
Treats web and flanges as plain rectangles. That is close for parallel-flange sections such as PFC and for plain cold-formed C-sections, and weakest for tapered-flange channels like the American C series, where the flange thins toward the toe. Fillet metal is excluded either way, so the true section weighs slightly more.
- Cross-sectional area
- 3.75 in²
They open the calculator with your figures already in it
Steel Channel (C-Shape) Weight Calculator: 12.77 lb/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Simplified channel cross-sectional area = 2×(flange width × flange thickness) + (depth − 2×flange thickness) × web thickness, the same rectangular-approximation method used for I-shapes; weight per unit length = area × steel density (7850 kg/m³)
Inputs used
- Overall Depth
- 7.75 in
- Flange Width
- 3 in
- Flange Thickness
- 0.33 in
- Web Thickness
- 0.25 in
Intermediate steps
- Cross-sectional area
- 3.75 in²
Confidence note: Treats web and flanges as plain rectangles. That is close for parallel-flange sections such as PFC and for plain cold-formed C-sections, and weakest for tapered-flange channels like the American C series, where the flange thins toward the toe. Fillet metal is excluded either way, so the true section weighs slightly more.
What this calculation does not cover
- Mass per unit length is not a grade. This page's own best case is a section measured off the steel with nothing stamped on it, and two channels of identical outline can be S235 and S355 — or merchant material folded into a channel rather than a structural section at all. That is up to a 50 per cent difference in yield strength which the four dimension fields cannot see, so matching a replacement member by weight matches its price and not its capacity.
- A channel loaded through its web twists as well as bends, because its shear centre sits outside the section behind the web — which is why channels get paired back to back, or restrained against rotation, where an I-section would not need it. Weight per unit length says nothing about that, and a purlin or trimmer picked off a weight table and left unrestrained rolls long before the steel is near its stress limit.
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This result is a specification — 12.8 lb/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Simplified channel cross-sectional area = 2×(flange width × flange thickness) + (depth − 2×flange thickness) × web thickness, the same rectangular-approximation method used for I-shapes; weight per unit length = area × steel density (7850 kg/m³)
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