A sheet metal gauge chart converts gauge numbers to actual thickness in inches and millimeters. Gauge systems vary by material — the same number means different thicknesses for steel, aluminum, and copper. Lower gauge numbers always indicate thicker metal. Use this chart to quickly look up thickness, compare materials, and calculate weight for fabrication, HVAC, automotive, and construction work.
Sheet Metal Gauge Reference
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Weight Calculator
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Common Applications by Gauge Range
How to Use the Sheet Metal Gauge Chart
Sheet metal gauge numbers are one of the most confusing aspects of metalworking — the same gauge number produces different thicknesses depending on the material. This sheet metal gauge chart covers all standard gauges for steel, aluminum, and copper from gauge 3 through 36, with thickness in both inches and millimeters, plus weight per square foot for quick material estimating.
Step 1: Select your material
Use the material tabs to filter to Steel, Aluminum, or Copper. When "All Materials" is selected, you'll see all three side by side for easy comparison. Steel uses the Manufacturers' Standard Gauge, while aluminum and copper use the Brown & Sharpe (American Wire Gauge) system — which is why the same gauge number means different thicknesses for each material.
Step 2: Find your gauge
Type a gauge number in the search box to jump straight to that row. You can also scroll the table or click any column header to sort. The table shows thickness in both inches and millimeters by default — use the unit toggle to display only one unit if you prefer a cleaner view. Lower gauge numbers always mean thicker material: 10 gauge steel is 0.1345" thick, while 26 gauge is only 0.0179".
Step 3: Calculate sheet weight
Use the Weight Calculator to estimate the weight of a cut piece. Select the gauge and material, then enter the width and length of your sheet in inches (or switch to mm). The calculator uses standard density values — 490 lb/ft³ for steel, 169 lb/ft³ for aluminum, and 559 lb/ft³ for copper — and returns weight in both pounds and kilograms. This is useful for shipping estimates, structural load calculations, and ordering stock by weight.
Understanding gauge numbers and thickness
The gauge system developed from the wire drawing industry, where higher numbers meant more drawing passes and thinner wire. When applied to sheet metal, lower gauge numbers indicate heavier, thicker material. This means gauge 3 steel at 0.2391" is roughly 20× thicker than gauge 30 at 0.0120". The most common gauges for general fabrication are 16 to 24, with 18 gauge being widely used for automotive work and 26 gauge for HVAC ductwork.
Steel vs. aluminum vs. copper gauges
Always confirm the material before specifying a gauge number on drawings or purchase orders. For example, 18-gauge steel is 0.0478" (1.214mm) thick, while 18-gauge aluminum is 0.0403" (1.024mm) — a 16% difference. Copper follows the same gauge system as aluminum in this range. In practice, specifying thickness in decimal inches or millimeters on engineering drawings avoids ambiguity entirely.
Weight per square foot reference
The weight per square foot column is useful for quick estimating. Steel at 18 gauge weighs approximately 2.000 lb/sq ft, aluminum weighs about 0.682 lb/sq ft at the same gauge, and copper weighs approximately 1.823 lb/sq ft. These values let you quickly estimate material cost and shipping weight for blanks and cut pieces without needing a scale.
FAQ
Is this sheet metal gauge chart free to use?
Yes, this sheet metal gauge chart is completely free. It runs entirely in your browser — no signup, no account, and no data is sent to any server. Bookmark it for quick shop reference.
Why does the same gauge number mean different thicknesses for steel vs aluminum?
Gauge systems are material-specific and historically developed separately. Steel uses the Manufacturers' Standard Gauge, while aluminum uses the Brown & Sharpe (American Wire Gauge) system. As a result, 16-gauge steel (0.0598") is thicker than 16-gauge aluminum (0.0508"). Always confirm the material when specifying a gauge number.
How do I calculate the weight of a sheet metal piece?
Multiply the area of your piece (in sq ft) by the weight per sq ft shown in the chart for your material and gauge. For example, a 2×4 ft piece of 16-gauge steel weighs 8 sq ft × 2.500 lb/sq ft = 20 lbs. The weight calculator section on this page does this math for you automatically.
What gauge is most common for HVAC ductwork?
HVAC ductwork typically uses 26-gauge (0.0179" / 0.455mm) galvanized steel for small ducts and 24-gauge (0.0239" / 0.607mm) for larger ducts and trunk lines. High-pressure systems may specify 22-gauge or heavier. Always refer to SMACNA standards for commercial work.
What gauge steel is used for car body panels?
Automotive body panels are typically 18-gauge to 20-gauge steel (0.0478"–0.0359" / 1.214mm–0.912mm). Structural reinforcements and floor pans may use 16-gauge or heavier. Aftermarket patch panels are commonly available in 18 and 20 gauge.
What is the thickest gauge number — is gauge 3 thicker than gauge 30?
Yes, lower gauge numbers mean thicker material. Gauge 3 steel is 0.2391" (about 6mm) thick, while gauge 30 is only 0.0120" (0.305mm). This counter-intuitive naming comes from the wire drawing process where more passes produce thinner wire with higher numbers.
What is the difference between galvanized and stainless steel gauges?
Standard steel gauge values apply to cold-rolled mild steel. Galvanized and stainless steel may have slightly different thicknesses at the same gauge due to coatings or alloy density differences. For precision fabrication, always confirm the actual thickness in inches or mm from your material supplier's spec sheet.
Can I use this chart for copper flashing or roofing sheet?
Yes. The copper column uses standard copper sheet gauge values (same as aluminum gauge in this range). For roofing, 16 oz copper is approximately 22-gauge (0.0216" / 0.549mm), while 20 oz is approximately 20-gauge. The oz-per-sq-ft weight labeling is common in roofing applications.