Metal Stud Gauge Chart: Gauge, Mils and Thickness

Steel stud gauge tells you how thick the steel is, and a lower gauge number means thicker steel. Non-structural interior studs are usually 25 gauge (18 mil) or 20 gauge drywall (30 mil); structural studs run 20 gauge (33 mil), 18 (43), 16 (54), 14 (68) and 12 (97). Specs and orders use mils, so the chart below converts both ways. Looking for depth, flange and length instead? See metal stud sizes & dimensions.

Metal stud gauge chart (gauge to mil to thickness)

One mil is 0.001 inch. Thicknesses are minimum base-metal values (before coating); the design thickness used by engineers is slightly higher (for example 0.0346" for 33 mil). Millimetre values are converted from the inch values and rounded. Stud gauge is not the same as sheet-metal gauge: an 18 gauge sheet is thicker than an 18 gauge (43 mil) stud, so use a stud chart, not a generic sheet-steel one.

What gauge means (and why higher is thinner)

Gauge is an old numbering system where a bigger number means thinner steel: 25 gauge is thinner than 20 gauge, which is thinner than 16 gauge. Because the numbers are only loosely tied to thickness, the industry specifies cold-formed framing in mils instead. In a part number like 362S162-43, the 362 is the web depth (3.62 in., a 3 5/8" stud), S162 is the 1 5/8" flange, and the 43 is the thickness in mils (about 18 gauge).

What each gauge is used for

• 25 ga (18 mil): ordinary non-structural interior partitions. The most common drywall stud.
• 20 ga drywall (30 mil): taller or heavier-finish non-structural walls, tile backer, higher impact areas. Thicknesses above 30 mil are generally treated as structural members.
• 20 ga structural (33 mil) and 18 ga (43 mil): load-bearing walls, exterior wall and curtain-wall backup, shorter structural framing. The engineer or spec sets which one.
• 16 ga (54 mil) and heavier: tall structural walls, headers, jambs and heavily loaded studs.
• Heavy fixtures and backing: cabinets, grab bars, TV mounts, handrails and similar loads are normally framed with heavier-gauge studs, doubled studs or added backing as shown on the drawings; do not assume a 25 ga stud will carry them.

Maximum wall height depends on gauge, stud depth, spacing, board type and deflection limit. Use the manufacturer's limiting-height tables for the actual number rather than a rule of thumb.

How to identify gauge on a stud

• Read the marking: studs are required to be marked with the manufacturer, the minimum steel thickness, and the yield strength or coating if they differ from the default (33 ksi, G40). The mark repeats along the web at roughly 8 ft or less.
• Check the end color on structural members: ClarkDietrich and CEMCO publish end-paint codes of white (33 mil), yellow (43), green (54), orange (68) and red (97). Non-structural studs are generally not color-coded, so rely on the stamp. Codes can differ by manufacturer, so confirm against the product data sheet.
• Read the legend: on a plan set, the wall type legend or general notes state the stud size and gauge; for a takeoff, that is the source of truth.
• Measure only as a last resort: use a caliper on bare steel, not the coated surface, and compare against the minimum values above.

Common mistakes with stud gauge

• Treating "20 gauge" as one thing. It can mean 30 mil drywall, 33 mil structural, or a gauge-equivalent (EQ) stud that is only 18 mil. Ask for the mil thickness.
• Substituting a thinner stud on a structural wall because it is the same depth. Same depth does not mean same capacity.
• Pricing the whole job at one gauge. Same depth, different gauge = different line items in the takeoff.
• Using a sheet-metal gauge chart for studs, which gives different thicknesses.
• Forgetting track. Track should match the stud depth and the thickness called out for the wall.

Frequently asked questions

What gauge are steel studs?

There is no single gauge. Non-structural interior drywall studs are usually 25 gauge (18 mil) or 20 gauge (30 mil). Structural, load-bearing studs start at 20 gauge structural (33 mil) and go up through 18 ga (43 mil), 16 ga (54 mil), 14 ga (68 mil) and 12 ga (97 mil).

What is the stud gauge for a standard interior partition?

Typically 25 gauge (18 mil) for ordinary non-structural partitions, or 20 gauge drywall (30 mil) for taller walls or heavier finishes. The wall type legend and spec section on the drawings set the actual requirement.

What are metal stud gauges, from thin to thick?

25 ga (18 mil), 20 ga drywall (30 mil), 20 ga structural (33 mil), 18 ga (43 mil), 16 ga (54 mil), 14 ga (68 mil), 12 ga (97 mil). A lower gauge number means thicker steel.

The gauge of a metal stud determines the ___ of the stud.

Thickness of the steel, and through that its strength: how much load it can carry, how tall a wall it can reach and how much it resists bending. It does not change the stud's depth (3 5/8 in. is still 3 5/8 in.).

How do I convert mil to gauge for a metal stud?

1 mil is one thousandth of an inch. Approximate stud pairings: 18 mil = 25 ga, 30 mil = 20 ga drywall, 33 mil = 20 ga structural, 43 mil = 18 ga, 54 mil = 16 ga, 68 mil = 14 ga, 97 mil = 12 ga. Gauge is only a reference; specs and orders should use mils.

Is a higher gauge number thicker?

No, the opposite. 16 gauge is thicker and stronger than 20 gauge, which is thicker than 25 gauge.

What is the difference between 20 gauge and 20 gauge EQ studs?

Conventional 20 gauge drywall studs are 30 mil and structural 20 gauge studs are 33 mil. Some manufacturers sell gauge-equivalent (EQ) studs labeled 20 ga that are only 18 mil, engineered with higher-strength steel to meet performance requirements. Always confirm the mil thickness.

Sources: ClarkDietrich Structural Design Guide and ProSTUD catalog; CEMCO product data (33-68 mil); ASTM C645 minimum thickness as summarized by Construction Specifier. Gauge is a reference only, so confirm thickness on the manufacturer's current data sheet before ordering.

Related: Metal stud sizes & dimensions · Reading a wall type legend · Free calculators · Glossary