Sheet Metal Gauge Chart 2026: 10-20 Gauge Steel, Stainless and Aluminum in mm

Use this sheet metal gauge chart to convert gauge numbers to actual thickness in inches and millimeters for mild steel, galvanized steel, stainless steel and aluminum. Lower gauge numbers mean thicker material, but each metal uses a different standard, so 18-gauge steel is not the same thickness as 18-gauge aluminum. For press brake bending, use the actual mm thickness to choose V-die opening, tonnage and minimum bend radius.

This guide covers sheet metal thickness conversions, gauge selection, press brake V-die opening, tonnage and bend radius. If you need a machine quote for a defined gauge range, prepare your material type, minimum and maximum thickness, bend length and production volume, then use the press brake quote page.

How the Sheet Metal Gauge System Works

The gauge system was developed when drawing wire through progressively smaller holes — each pass through a die was one "gauge." The more passes, the thinner (higher gauge number) the wire. When the system was adapted for sheet metal, the convention remained: higher gauge = thinner material.

Here's what makes the gauge system confusing: there is no single universal standard. Different metals follow different gauge systems:

• Manufacturers' Standard Gauge (MSG): Used for ferrous metals — mild steel, galvanized steel, stainless steel
• Brown & Sharpe (B&S) / American Wire Gauge (AWG): Used for non-ferrous metals — aluminum, brass, copper
• Birmingham Wire Gauge (BWG): Used in some industries for steel and aluminum

Mild Steel (Carbon Steel) Gauge Chart

Mild steel (low-carbon steel) is the most common sheet metal for press brake fabrication. It uses the Manufacturers' Standard Gauge (MSG). The values below are based on ASTM A1008 standards.

Galvanized Steel Gauge Chart

Galvanized steel has a zinc coating applied after rolling, which adds slightly to the total thickness. Galvanized steel gauges are very similar to mild steel but with a small offset due to the zinc layer. Commonly used in HVAC ductwork, roofing, and outdoor enclosures.

Stainless Steel Gauge Chart

Stainless steel also uses the Manufacturers' Standard Gauge but with different actual thicknesses than mild steel. Stainless steel is harder and more springback-prone than mild steel, requiring special attention to tooling and tonnage when bending on a CNC press brake.

Aluminum Gauge Chart

Aluminum uses the Brown & Sharpe (B&S) gauge system, which is different from the steel gauge system. Aluminum is significantly lighter than steel — for the same gauge number, aluminum is thinner than steel. Aluminum also requires larger minimum bend radii due to its tendency to crack at tight bends.

How Sheet Metal Gauge Affects Press Brake Bending

For press brake operators, gauge isn't just a number on a purchase order — it directly determines your tooling selection, V-die opening, bending force (tonnage), and minimum bend radius. Understanding these relationships is fundamental to setting up accurate and safe bending operations.

V-Die Opening Selection by Thickness

The standard rule for V-die selection is: V-die opening = 8× material thickness for mild steel. Adjust for other materials:

Press Brake Tonnage Guide by Gauge

The following values are approximate bending force for a 1-meter bend length using air bending with an 8× V-die. Actual tonnage depends on material tensile strength, V-die opening, and bend length. Use our press brake bending calculator for precise values.

Minimum Bend Radius by Material and Gauge

Bending too tightly will crack or weaken the material. The minimum inside bend radius depends on both the material type and thickness (gauge). Below are typical minimum inside bend radii for 90° bends:

These values assume standard grain direction (bending perpendicular to grain). Bending parallel to grain increases cracking risk — increase minimum radius by 50% when bending parallel to the rolling direction on aluminum and stainless steel.

For a deeper dive into bending calculations, see our guides on press brake tonnage calculation and CNC bending angle compensation.

Choosing the Right Gauge for Your Application

Gauge selection is a balance between structural requirements, weight, formability, and cost. Here are industry-standard gauge recommendations by application:

Quick Selection Tips

• For structural parts: Use 10–14 gauge mild steel — provides rigidity without excessive weight
• For precision enclosures: Use 14–16 gauge — easy to bend on a CNC press brake with consistent results
• For outdoor/corrosive environments: Upgrade to galvanized or 304 stainless steel in the same gauge range
• For lightweight assemblies: 5052 or 6061 aluminum at 16–18 gauge is an excellent substitute for steel
• Going thinner than 22 gauge: Extra care is needed — thin material is prone to warping during bending and welding

Conclusion

Sheet metal gauge is a foundational concept for anyone working in metal fabrication. The key takeaways: lower gauge = thicker metal, different metals use different gauge systems, and always verify actual thickness in millimeters or inches with your supplier before programming your press brake.

For press brake operators, gauge directly determines your V-die selection, required tonnage, and minimum bend radius. Using this guide alongside our bending calculator and press brake setup guide will help you set up accurate bends every time.

Need help selecting the right press brake for your material thickness range? Use the press brake quote page and include your gauge range, material type, bend length, drawing, tooling needs and production volume. Rucheng Machinery supplies CNC press brakes ranging from compact models to 1600-ton heavy-duty machines, with tooling packages matched to your sheet thickness range.