This is a straightforward measurement taken with a tape measure or large caliper. Here are the tools you will need: Tape Measure or Ruler: For measuring the length and key dimensions like height, width, and thickness. Related: Structural A36 Steel Channel Section Properties Table Chart Related Resources:H: The height of the channel from the bottom of the flange to the top (also referred to as the “web height”). t: The thickness of the web (the vertical section of the channel).