By the LGS FrameX Team · Updated October 2026
If you are new to light gauge steel framing, the first thing to learn is how thickness is described. Steel studs are specified by gauge or by mil, and the two systems do not map perfectly onto each other. This guide explains both in plain language, shows common thicknesses, and explains how thickness relates to where a stud can be used. It is a companion to our complete guide to light gauge steel framing.
What does gauge mean for steel studs?
Gauge is a traditional number used to describe sheet metal thickness. The important rule is that a lower gauge number means thicker steel. A 12 gauge stud is much heavier than a 25 gauge stud. Gauge is easy to say, but it is not exact, because different metals and standards use different gauge tables.
What is a mil?
For cold-formed steel framing in the United States, the more precise way to describe thickness is the mil. One mil is one thousandth of an inch (0.001 in). A 33 mil stud has a minimum base steel thickness of about 0.033 inches, or roughly 0.84 millimeters. Engineers and detailers prefer mils because they appear directly in structural tables and drawings.
Common thicknesses at a glance
| Approximate gauge | Mil designation | Approximate thickness (mm) | Typical use |
|---|---|---|---|
| 25 ga | 18 mil | 0.46 | Non-structural interior partitions |
| 22 ga | 27 mil | 0.69 | Light non-load-bearing walls |
| 20 ga | 33 mil | 0.84 | Non-load-bearing and light structural walls |
| 18 ga | 43 mil | 1.09 | Load-bearing walls in low-rise buildings |
| 16 ga | 54 mil | 1.37 | Load-bearing walls, floor joists |
| 14 ga | 68 mil | 1.73 | Heavier walls and joists, taller buildings |
| 12 ga | 97 mil | 2.46 | Heavy structural framing in mid-rise buildings |
These values are typical industry references. Exact thicknesses, coatings and permitted uses vary by manufacturer, product standard and local code, so always rely on the engineer’s drawings for your project.
Structural and non-structural framing
Non-structural (non-load-bearing) studs form interior partitions and carry only their own weight and light loads such as drywall and wall-mounted items. They are usually the thinnest studs.
Structural (load-bearing) studs carry loads from floors, roofs and walls above down to the foundation. They are thicker, are specified by an engineer and must be installed with the connections, bracing and fasteners shown on the drawings.
Stud dimensions beyond thickness
Thickness is only one part of the profile. A stud is also defined by its web depth (the wide face), flange width, lip size and punchouts for services. Common web depths in framing include 2-1/2, 3-5/8, 4, 6 and 8 inches, with larger sizes used for floor joists and heavier walls. Tracks are the U-shaped channels at the top and bottom of a wall that hold the studs in place.
How to choose the right thickness
- Know the building height and type. A single-family home and an eight-storey building need very different members.
- Check loads and code. Wind, seismic, snow and floor loads all change the required thickness and spacing.
- Follow the engineer of record. The structural engineer selects member sizes, thickness, spacing and connections.
- Plan production early. Your roll-forming equipment must be able to run the thicknesses your projects need.
Thickness range of FrameX Fx series machines
The FrameX Fx series of LGS roll-forming machines covers different thickness ranges so that you can match the machine to your projects. The Fx01 and Fx03 handle 24 to 16 gauge (0.6 to 1.5 mm) material, suited to residential and mixed-use builds. The Fx06 and Fx08 handle 21 to 12 gauge (0.8 to 2.5 mm) material for heavier structural framing in commercial and mid-rise work. All models run at up to 30 meters per minute. See the full machine range or the individual pages for the Fx01, Fx03, Fx06 and Fx08.
Frequently asked questions
Is a lower gauge number thicker or thinner?
A lower gauge number means thicker steel. A 12 gauge stud is much thicker than a 25 gauge stud.
What is a 33 mil stud?
A 33 mil stud has a base steel thickness of about 0.033 inches, roughly 0.84 millimeters, which is close to 20 gauge.
Which thickness is used for load-bearing walls?
It depends on the building and the engineering. Load-bearing walls in low-rise buildings often use mid-range thicknesses, and taller buildings use heavier ones. Your structural engineer specifies the correct size.
Talk to LGS FrameX about your project
Tell us your building type, height and timeline, and our team will help you choose the right light gauge steel framing approach or Fx series machine.
