Sheet Metal Gauge Thickness Chart: Steel, Aluminum, Stainless & More

A sheet metal gauge number tells you how thick a piece of metal is — but the same gauge number means a different thickness depending on whether the material is steel, aluminum, stainless steel, or brass. Ordering “16 gauge” without specifying the material can result in parts that are off by 15–20% in thickness, which is well outside the tolerance range for most designs.

The charts below convert gauge numbers to exact thickness values in both inches and millimeters for every common sheet metal material. This guide also covers the ASTM tolerance ranges that govern what thickness you actually receive, the weight-per-area values needed for logistics planning, and the gauge ranges suited to specific sheet metal fabrication applications.

What Is Sheet Metal Gauge?

Gauge is a numbering system that specifies sheet metal thickness. A higher gauge number indicates a thinner sheet — 24 gauge is thinner than 16 gauge, and 16 gauge is thinner than 10 gauge. This counterintuitive relationship exists because the system originated from the wire-drawing industry, where each successive pass through a die made the wire thinner and added one to the gauge count. More drawing passes produced a thinner wire with a higher gauge number.

The critical detail that catches many engineers: gauge is not a universal standard. Three separate gauge systems are in active use, each governing different metals:

✅ Sources: ASTM A568/A568M (carbon steel), ASTM B209 (aluminum), ASTM A480 (stainless steel)

Because these three systems were developed independently and never unified, a 16-gauge measurement yields different thicknesses: 0.0598″ for mild steel (MSG), 0.0625″ for stainless steel (SS Gauge), and 0.0508″ for aluminum (B&S/AWG). That is a 0.0117″ spread — more than enough to cause press brake setup failures, weld penetration miscalculations, and assembly fit issues.

Complete Gauge Thickness Chart (All Materials)

The consolidated chart below shows the thickness of each gauge number across all six common sheet metals, allowing side-by-side comparison in a single reference. All values are nominal thickness in inches, with millimeter equivalents in parentheses. KUSLA Prototype uses this multi-material chart during design review to verify that customer drawings specify the correct gauge-to-decimal conversion for the ordered material.

✅ Mild steel: Manufacturers’ Standard Gage per ASTM A568. Stainless: SS Gauge per ASTM A480. Aluminum/Brass: Brown & Sharpe (AWG) per ASTM B209/B36. Galvanized: MSG + zinc coating allowance per ASTM A653. Copper: AWG per ASTM B152.

Notice that brass and aluminum share identical gauge values — both use the Brown & Sharpe system. Copper uses the same AWG system but with slightly different nominal values reflecting its higher density. Galvanized steel is consistently thicker than bare mild steel at the same gauge number because the gauge specification accounts for the zinc coating layer (G90 galvanizing adds approximately 0.0037″ total to the base steel thickness).

Mild Steel Gauge Chart

Mild (carbon) steel uses the Manufacturers’ Standard Gage (MSG), which defines thickness based on weight: 41.82 pounds per square foot per inch of thickness. This means gauge values for steel can be derived mathematically from weight, unlike the empirical AWG system used for non-ferrous metals. The MSG system governs standard carbon steels including 1008, 1010, 1018, and 1020 grades in both hot-rolled and cold-rolled conditions.

✅ Thickness: Manufacturers’ Standard Gage per ASTM A568/A568M. Weight calculated as thickness (in) × 41.82 lb/ft²/in.

The weight column is useful for shipping cost estimation. KUSLA Prototype ships sheet metal parts globally via air freight, and accurate weight data prevents discrepancies between quoted and actual logistics costs — particularly for large-panel parts where a single gauge step changes the shipping weight by 15–25%.

Stainless Steel Gauge Chart

Stainless steel follows its own gauge table, separate from the MSG system used for carbon steel. At every gauge number, stainless steel is slightly thicker than mild steel — for example, 18-gauge stainless measures 0.0500″ compared to 0.0478″ for mild steel, a difference of 0.0022″. This reflects the fact that the stainless gauge system was developed to account for stainless steel’s higher density (approximately 8.0 g/cm³ for 304 vs 7.85 g/cm³ for carbon steel). The chart applies to all austenitic grades including 304 and 316, as well as ferritic and martensitic grades.

✅ Source: Stainless Steel Gauge table per ASTM A480/A480M

Aluminum Gauge Chart

Aluminum uses the Brown & Sharpe gauge system (also called American Wire Gauge / AWG), which was originally designed for wire-drawing and follows a geometric progression. At any given gauge number, aluminum is significantly thinner than steel — 18-gauge aluminum measures 0.0403″ versus 0.0478″ for steel, a 15.7% difference. This chart applies to all wrought aluminum alloys commonly used in sheet metal fabrication, including 1100, 3003, 5052, and 6061.

✅ Thickness: Brown & Sharpe (AWG) per ASTM B209. Weight calculated using aluminum density 0.098 lb/in³ (2.71 g/cm³).

Aluminum’s lower density makes weight especially relevant for aerospace and portable equipment applications. A 16-gauge aluminum panel weighs approximately 71% less than a 16-gauge mild steel panel of the same area — not just thinner, but lighter per unit thickness as well. KUSLA Prototype machines and bends aluminum sheet in gauges from 8 through 26 for enclosures, brackets, and chassis components.

Galvanized Steel Gauge Chart

Galvanized steel gauge numbers follow the MSG system like bare mild steel, but the nominal thickness at each gauge is slightly greater. The difference accounts for the zinc coating applied to the base steel. A standard G90 galvanized coating adds approximately 0.90 oz/ft² of zinc per side, which translates to roughly 0.0017″–0.0019″ of additional thickness per side. The chart below reflects nominal galvanized thickness per ASTM A653/A653M.

✅ Source: ASTM A653/A653M. Values reflect G90 hot-dip galvanized nominal thickness.

Brass & Copper Gauge Charts

Brass uses the Brown & Sharpe (AWG) gauge system — the same system as aluminum. This means brass and aluminum share identical gauge-to-thickness values across the entire range. Copper also uses the AWG system but carries slightly different nominal values at each gauge number, reflecting copper’s higher density (8.96 g/cm³ vs brass at ~8.5 g/cm³). Dimensional standards are governed by ASTM B36 for brass and ASTM B152 for copper.

Brass Gauge Chart

✅ Source: Brown & Sharpe (AWG) per ASTM B36

Copper Gauge Chart

✅ Source: AWG per ASTM B152

Sheet Metal Weight Reference

Weight-per-area data is essential for two tasks that happen after material selection: structural calculations (dead load contributions in panels and enclosures) and logistics budgeting (shipping cost estimation for air and sea freight). The table below provides quick-reference weight values for the two most commonly fabricated sheet metals. Weight is calculated from nominal thickness and published material density.

✅ Steel: thickness × 41.82 lb/ft²/in (density 7.85 g/cm³). Aluminum: thickness × 14.05 lb/ft²/in (density 2.71 g/cm³).

Gauge Tolerances: What ASTM Standards Actually Allow

Gauge charts list nominal thickness, but the sheet you receive from the mill will not be exactly that number. ASTM standards define allowable thickness tolerances that vary by material, gauge, and sheet width. Understanding these tolerances prevents surprises during fabrication — a press brake set up for nominal 0.0299″ (22 gauge) mild steel may see material arriving anywhere from 0.0269″ to 0.0329″ depending on the mill and sheet width.

✅ Sources: ASTM A568, A480, B209, B152, B36. Tolerance ranges shown for 48″-wide sheet; narrower sheets have tighter tolerances.

Wider sheets have larger tolerances because rolling mills have more difficulty maintaining uniform thickness across greater widths. For tight-tolerance applications, specifying a narrower sheet width or requesting mill-certified test reports (MTRs) confirming actual measured thickness is standard practice. KUSLA Prototype verifies incoming material thickness with digital calipers at multiple points across the sheet before beginning fabrication on precision projects.

Sheet vs Plate: Where Gauge Ends

The gauge system applies only to sheet metal — not plate. The industry-standard boundary between sheet and plate varies slightly by material but follows consistent conventions. Once a metal piece exceeds the sheet threshold, it is specified by decimal thickness or fractional inches, never by gauge number.

Metal thicker than 6 mm is generally classified as plate and is machined or fabricated using different processes — plasma cutting, oxy-fuel cutting, and heavy press brakes rather than standard sheet metal shears and lighter-tonnage brakes. Gauge numbers become meaningless above this threshold. For heavy-gauge projects that cross into plate territory, KUSLA Prototype routes parts through CNC machining workflows rather than sheet metal fabrication lines.

Gauge Selection by Application

Different industries and product categories cluster around specific gauge ranges based on their balance of structural requirements, weight constraints, and forming feasibility. The table below maps common applications to their typical gauge ranges and explains why each range suits its purpose.

These ranges are starting points — the final gauge selection depends on the specific load case, forming complexity, and surface finish requirements of each part. KUSLA Prototype’s engineering team evaluates gauge selection during design-for-manufacturing review, recommending gauge adjustments when the specified thickness creates forming problems (cracking at bends, excessive springback, or insufficient stiffness without reinforcing features).

Common Gauge Mistakes to Avoid

The gauge system’s legacy origins and multiple parallel standards create several recurring errors that waste material, delay production, and require costly rework. Each of the following mistakes occurs frequently enough that fabrication shops treat them as expected — but they are entirely preventable with correct specification practices.

Using the Wrong Gauge Table for the Material

Ordering “10 gauge” stainless steel while referencing a mild steel gauge chart means expecting 0.1345″ but receiving 0.1406″ — a 0.006″ difference. For press brake bending, this error changes the required tonnage by 8–12% and shifts the inside bend radius, potentially causing cracking or out-of-spec bend angles. Always confirm which gauge system (MSG, SS Gauge, or AWG) applies to the material being ordered.

Treating Gauge as a Universal Measurement

Writing “16 gauge” on a drawing without specifying the material is ambiguous. That callout maps to 0.0598″ in mild steel, 0.0625″ in stainless, or 0.0508″ in aluminum — three different parts. The solution is to always call out both the material and the decimal equivalent: “16 ga mild steel (0.060″).”

Confusing Birmingham Wire Gauge with Sheet Metal Gauge

The Birmingham Wire Gauge (BWG) is a wire gauge system, not a sheet metal gauge system. BWG values differ from MSG, SS Gauge, and AWG at every gauge number. At least one widely-referenced online guide incorrectly applies BWG values to all sheet metals. If a reference chart mentions “BWG” or “Birmingham,” it is a wire reference and should not be used for sheet metal thickness specification.

Specifying Gauge on Metric-Only Drawings

Gauge is a North American convention. International suppliers — particularly in Asia and Europe — work exclusively in millimeters. Sending a drawing that says “18 gauge” to a Chinese or German supplier without the millimeter equivalent invites interpretation errors. The best practice for international procurement is to specify thickness in millimeters only, with the gauge number in parentheses as a secondary reference if needed.

How Gauge Affects Sheet Metal Fabrication

Gauge thickness directly determines the forming parameters, tooling selection, and process feasibility of every sheet metal fabrication operation. Understanding these relationships prevents specifying a gauge that is technically correct for the structural requirement but impractical to manufacture.

Bending: Minimum Bend Radius Scales with Thickness

The minimum inside bend radius for any sheet metal part is a function of the material thickness and the material’s ductility. The general rule for mild steel is that the minimum bend radius equals 1× the material thickness (1T) for soft tempers, increasing to 2T–3T for harder tempers and higher-strength alloys. A 14-gauge mild steel sheet (1.897 mm) requires a minimum inside bend radius of approximately 1.9 mm; attempting a tighter radius risks cracking at the outside of the bend. Aluminum alloys are less forgiving — 6061-T6 typically requires 2T–3T minimum bend radius, while softer 5052-H32 allows 1T bends at most gauges.

For a detailed bend radius reference by material and gauge, see KUSLA Prototype’s sheet metal bend radius chart (coming soon).

Welding: Gauge Determines Heat Input Limits

Thinner gauges (20 gauge and above) require lower welding heat input to avoid burn-through, warping, and excessive heat-affected zone (HAZ) width. Tack welding techniques become critical for thin-gauge assemblies. At 22–26 gauge, pulse MIG or TIG with low-amperage settings is standard; below 24 gauge, resistance spot welding or laser welding often replaces arc welding entirely because the thermal input is more precisely controllable.

Laser Cutting: Maximum Thickness Varies by Material

Fiber laser cutting machines — the standard in modern sheet metal shops — handle different maximum thicknesses depending on the material. Mild steel can be laser-cut up to approximately 25 mm, but for sheet metal work the practical range is 7–20 gauge (0.036″–0.179″). Aluminum reflects more laser energy and is typically limited to thinner gauges for clean edge quality. Stainless steel’s higher melting point allows consistent cuts across a wide gauge range. At very thin gauges (26+), the heat from cutting can cause distortion unless the nesting layout and cut sequence are optimized.

Forming Complexity: Thicker Gauges Limit Feature Count

Thicker sheet (10–14 gauge) can handle fewer formed features per part — each bend, louver, or emboss requires higher tonnage and places more stress on adjacent features. Thin gauges (20–24) accept complex forming with multiple bends, but they are more susceptible to springback (the material’s tendency to partially return to its flat state after bending), requiring overbend compensation in the press brake program. KUSLA Prototype’s fabrication team accounts for springback when programming CNC press brakes, adjusting the bend angle by 1°–5° depending on material type and gauge.