Sheet metal thickness in the United States is commonly specified by gauge number rather than direct measurement. The gauge system is a legacy from the wire and sheet metal industries, and it remains the standard way to order coil stock and specify material thickness on engineering drawings for stamped and fabricated parts.

For alloy selection guidance, see our aluminum stamping alloy selection guide.

The critical detail that many engineers miss: gauge numbers do not convert to the same thickness for different metals. 16 gauge steel, 16 gauge stainless steel, and 16 gauge aluminum all have different actual thicknesses. This article provides complete gauge-to-thickness conversion tables for the three most commonly stamped metals, along with practical guidance for specifying thickness in metal stamping projects.

Steel Sheet Metal Gauge Chart (Standard Gauge / Manufacturers’ Standard)

Carbon steel uses the Manufacturers’ Standard Gauge, which is based on weight per square foot. This is the most commonly referenced gauge system in metal stamping.

Most common gauges for steel stamping: 16-26 gauge (0.0598-0.0179 inches) covers the majority of stamped steel parts including brackets, clips, enclosures, and structural components.

Stainless Steel Gauge Chart

Stainless steel does not follow the Manufacturers’ Standard Gauge used for carbon steel. Instead, it uses its own gauge-to-thickness conversion. Note that for the same gauge number, stainless steel is slightly thinner than carbon steel.

Aluminum Sheet Metal Gauge Chart (Brown & Sharpe / AWG)

Aluminum uses the Brown & Sharpe (B&S) gauge system, also known as the American Wire Gauge (AWG). The same gauge numbers produce significantly different thicknesses than steel or stainless steel.

Why Gauge Numbers Differ Between Metals

The gauge systems developed independently for different metals based on different standards:

• Steel uses the Manufacturers’ Standard Gauge for Sheet Steel, where gauge numbers are based on the weight of the sheet per square foot (1 gauge unit = 2.5 pounds/ft2 starting from 0000 gauge). This system was defined by US federal law in 1893.
• Stainless steel uses a separate system with slightly different thickness values that do not follow a weight-based formula.
• Aluminum uses the Brown & Sharpe (American Wire Gauge) system, originally developed for wire drawing. The progression follows a geometric series where each increase of 6 gauge numbers halves the cross-sectional area.

Quick comparison at 16 gauge:

This difference matters in metal stamping: die clearances, tonnage calculations, and springback predictions all depend on actual material thickness, not gauge number. Always verify the actual decimal thickness when switching materials.

Gauge Selection for Metal Stamping

Choosing the right gauge depends on the part’s structural requirements, forming severity, and cost targets:

Thin Gauge (26-30 gauge / 0.010-0.018 inches)

• Electrical contacts, shielding cans, battery contacts
• Easy to stamp at high speed, low tonnage requirements
• Susceptible to distortion during handling
• Used extensively in electronics stamping

Medium Gauge (18-24 gauge / 0.024-0.048 inches)

• The sweet spot for most stamped parts: brackets, clips, enclosures, covers
• Good balance of stampability, strength, and cost
• Compatible with all stamping processes: progressive, compound, and single-operation dies

Heavy Gauge (10-16 gauge / 0.060-0.135 inches)

• Structural brackets, automotive chassis parts, construction hardware
• Requires higher press tonnage and more robust tooling
• Springback becomes more significant
• Often stamped on hydraulic presses or heavy mechanical presses

Plate (7-9 gauge / 0.135-0.180+ inches)

• Heavy structural components, base plates, mounting brackets
• Requires high-tonnage presses (200+ tons)
• Limited forming capability – simple bends and blanking operations
• Alternative: laser cutting + CNC brake forming may be more economical at low volumes

Specifying Thickness on Drawings

Best practice for engineering drawings and RFQ packages:

• Always include the decimal thickness (e.g., “0.048 inches” or “1.2mm”), not just the gauge number
• Specify thickness tolerance for critical applications (e.g., “0.048 +/-0.003 inches”)
• Include the material with the gauge if using gauge numbers (e.g., “18 gauge CRS” not just “18 gauge”)
• Reference the standard when it matters: “per ASTM A1008” for carbon steel sheet

Specifying decimal thickness eliminates the confusion caused by different gauge systems and ensures your stamping supplier uses the correct material.

Thickness Tolerances for Sheet Metal

Sheet metal coil stock comes with standard mill tolerances that vary by thickness and material:

These are typical commercial tolerances. Tighter tolerances are available from precision re-rollers at additional cost. In stamping, material thickness variation directly affects part dimensions – particularly bend angles and drawn depths.

Need Help Specifying Material for Your Stamped Parts?

Our engineering team can recommend the optimal gauge, material grade, and temper for your application based on structural requirements, forming needs, and cost goals. Send us your part design for a free manufacturability review.

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