Channel Weight Calculator (ISMC / MC)

How ISMC Channel Weight Is Calculated

ISMC (Indian Standard Medium Weight Channel) sections have a C-shaped cross-section — two flanges projecting from one side of the web, unlike I-beams where flanges extend on both sides. The inner root radius between the web and flanges, and the tapered flange edges, mean that a simple rectangular cross-section calculation will underestimate the actual weight.

This calculator offers two sets of unit weights: the ISMC nominal values from IS 808 / SP 6(1) (used in design books and most drawings), and the MC series weights published by SAIL and JSPL for the channels they actually roll today (e.g. MC 100×50×5 = 9.56 kg/m vs ISMC 100 = 9.2 kg/m). For purchase and billing, use the series and dimensions your supplier quotes. The formula is: Total Weight (kg) = Unit Weight (kg/m) × Length (m). For example, ISMC 200 has a unit weight of 22.1 kg/m, so a 6 metre piece weighs 22.1 × 6 = 132.6 kg.

One important property of channels is that their shear centre does not coincide with the centroid — it lies outside the web on the open side. A transverse load applied through the centroid will cause the channel to twist unless it is laterally braced. This is why channels are often used in pairs (back-to-back or toe-to-toe) or as purlins bolted to sheeting that provides continuous lateral restraint.

Worked Example — ISMC 150 Purlins for an Industrial Shed

An industrial shed (30m length) with purlins at 1.4m spacing on each slope — 22 purlins per slope, 6m purlin length:

• ISMC 150 unit weight = 16.4 kg/m
• Weight per 6m purlin = 16.4 × 6 = 98.4 kg
• Total purlins = 22 × 2 slopes = 44 pieces
• Total purlin weight = 98.4 × 44 = 4,329.6 kg (4.33 tonnes)
• Add ~5% for sag rods and cleat connections ≈ 4,546 kg

ISMC Channel Weight Chart — Complete IS 808 Reference

All standard ISMC channel sizes from ISMC 75 to ISMC 400, with depth, flange width, weight per metre, and weight per standard length. These values are used for material estimation, procurement, and transport planning.

Source: IS 808 / SP 6(1) nominal ISMC table (each value cross-checked as sectional area × 0.785). Mill-rolled MC series (SAIL/JSPL) weights: MC 75 = 7.14, MC 100 = 9.56, MC 125 = 13.1, MC 150 = 16.8, MC 175 = 19.6, MC 200 = 22.3, MC 250 = 30.6, MC 300 = 36.3, MC 400 = 50.1 kg/m.

Common Applications of ISMC Channels

The primary use of ISMC channels is as roof purlins in industrial sheds. ISMC 125 to ISMC 200 are the standard purlin sizes for spans of 4–7m between trusses. Purlins are bolted to the top chord of roof trusses using cleat angles and support the roof sheeting (GI or colour-coated profile sheets).

Wall girts (horizontal members supporting wall cladding) are another major application — typically ISMC 100 to ISMC 150. In multi-storey buildings, channels serve as stair stringers, lift shaft framing, and edge beams for composite metal deck floors. Two channels placed back-to-back with a gap form a built-up I-section usable as a column or beam, commonly seen in lattice towers and portal frames.

In mechanical and plant engineering, channels are used as equipment base frames, conveyor supports, pipe rack members, and cable tray supports. The flat web allows bolting other components directly without additional gusset plates. ISMC 200 and ISMC 250 are popular for skid-mounted equipment frames where portability is needed.

ISMC vs ISLC — Which Channel Section to Use?

IS 808 defines two channel types: ISMC (Medium Weight) and ISLC (Light Weight). ISMC has thicker flanges and web compared to ISLC of the same depth, resulting in higher weight per metre but also higher load capacity. For example, ISMC 150 weighs 16.4 kg/m with 9.0mm flange thickness, while ISLC 150 weighs 14.4 kg/m with 7.8mm flange thickness — about 12% lighter.

In practice, ISMC is overwhelmingly more popular and readily available at steel stockists. ISLC sections are harder to source and are used only when the designer specifically needs to minimize self-weight — such as long-span purlins where dead load reduction is critical, or prefabricated lightweight structures. For most construction projects, specifying ISMC is the more practical and available choice.