Complete Sheet Metal Gauge-to-Thickness Chart

Galvanized Sheet Metal Thickness

These are illustrative ranges based on common G90 coating-mass conversions, not certified dimensional values. See the dedicated galvanized section below for the coating-designation explanation.

Important Conversion Notes

• Values shown are nominal, conventional, published gauge equivalents, not exact measured thicknesses.
• Gauge systems differ by material: mild steel, stainless steel, and aluminum each commonly use their own conventional series.
• Actual purchased thickness depends on the order specification, applicable ASTM standard, and manufacturing tolerances.

• Gauge number: The traditional designation printed on mill documentation or used in ordering.
• Nominal thickness: The conventional published thickness associated with that gauge number.
• Actual measured thickness: What a caliper or micrometer records on a specific sheet.
• Base metal thickness: The steel substrate thickness before any coating is applied.
• Coated thickness: The finished thickness of a sheet including its metallic or paint coating.

Gauge is a dimensional designation, not a direct statement of material strength, corrosion resistance, or suitability for a particular construction application.

Why Higher Gauge Numbers Mean Thinner Metal

Using the ordinary mild steel series as an illustration, 10-gauge steel (0.1345 in.) is thicker than 16-gauge steel (0.0598 in.), which is thicker than 22-gauge steel (0.0299 in.). This inverse relationship traces back to historical wire and sheet drawing processes, though not every modern gauge series follows the same mathematical progression.

These values are labeled by system, not presented as an ASTM-prescribed universal gauge thickness. ASTM material specifications govern the actual ordered product.

Fractional-inch equivalents are rounded approximations, not exact substitutes for the decimal gauge thickness. Weight figures use a 490 lb/ft³ steel density approximation.

Do not treat this as an exact result for every G30, G60, G90 or other product. If a legacy galvanized conversion table is used elsewhere, identify the convention and keep it distinct from certified product dimensions per the actual mill certification.

ASTM A480/A480M governs applicable general product requirements and tolerances, while the specific stainless material specification governs the ordered product. Grades such as 304, 316 and 430 are not different gauge systems; grade affects material properties, and the nominal gauge table remains a separate conversion convention. See the Structural Steel Weight Chart for structural member weight, which is distinct from sheet weight.

ASTM B209/B209M aluminum orders should specify the applicable alloy, temper, actual nominal thickness, and dimensional requirements rather than a gauge number alone.

Equal gauge numbers cannot be assumed to provide equivalent structural performance; each material has different yield strength, tensile strength and elastic modulus, so a matching thickness does not guarantee matching capacity.

Establishing the intended gauge convention before ordering material is essential; specifying “16 gauge” without identifying the applicable system and material leaves room for a costly misunderstanding.

Precise converted values differ from rounded metric equivalents seen in some tables; use the exact conversion for manufacturing tolerance calculations.

The nearest gauge is not necessarily the manufacturer’s actual ordered designation; use it only as an approximation aid.

1/16 inch is exactly 0.0625 inch, while conventional 16-gauge mild steel is nominally 0.0598 inch; they are close, not identical. A nearby gauge number should never be treated as an exact fractional-inch size.

10-, 12- and 14-Gauge

These heavier gauges (0.1345, 0.1046 and 0.0747 in. in mild steel) are common in structural brackets, heavy equipment panels and fabrication requiring higher stiffness, subject to the actual design requirements.

16- and 18-Gauge

Sixteen-gauge (0.0598 in. mild steel) and 18-gauge (0.0478 in. mild steel) are common in general fabrication, enclosures, and lighter structural panels. A focused comparison: 14-gauge (0.0747 in.) is noticeably thicker than 16-gauge, which is in turn thicker than 18-gauge, useful context for fabricators choosing between adjacent gauges.

20-, 22-, 24- and 26-Gauge

These lighter gauges are common in ductwork, roofing panels, and light cladding, always subject to the applicable design, manufacturer span table, or code requirement rather than gauge number alone.

• Material specification: Different ASTM specifications apply different tolerance rules.
• Hot-rolled or cold-rolled production: Production method affects achievable tolerance.
• Sheet width: Wider sheets can carry different tolerance allowances than narrower ones.
• Ordered thickness: The specific decimal thickness ordered, not just the nearest gauge.
• Product category: Structural, commercial or other quality categories can carry different tolerances.

ASTM A568/A568M contains dimensional tolerance provisions for applicable steel sheet products, while ASTM A480/A480M has separate requirements for stainless steel. There is no single generic universal tolerance, such as plus or minus 0.005 inch, that applies to every sheet and width; the applicable standard and product category govern.

A micrometer measurement across a coated sheet may not represent its base-metal thickness alone; the reading includes any metallic and paint coating. Coating mass designations such as G60 or G90 classify coating weight, not a stated coating thickness on each face.

A material specification, a general dimensional tolerance standard, and a traditional gauge chart each play a different role; ASTM material specifications are not interchangeable with traditional gauge conversion tables. For plate-specific thickness beyond sheet gauge, see the related Steel Plate Thickness Chart.

• Yield strength: Varies significantly between low-carbon steel, structural steel, stainless steel and aluminum alloys.
• Tensile strength: Affects ultimate load capacity before failure.
• Elastic modulus: Affects stiffness and deflection under load.
• Sheet thickness, panel geometry, unsupported span and load direction all combine with material properties to determine actual capacity.

Detailed structural member design for beams, angles and tubing remains on the dedicated Structural Steel Shapes Chart, Steel Square Tube Size Chart, and HSS Size Chart, which cover structural sections rather than sheet gauge.

For example, 16-gauge mild steel at 0.0598 inch is approximately 2.44 lb/ft² using a steel density of 490 lb/ft³. Coating and different alloy densities change the finished-sheet weight; these are clearly identified approximations, not certified weights. Use the Steel Weight Calculator for project-specific totals.

• Sheet size: The cut length and width of a flat sheet.
• Thickness: The dimensional measurement in inches or mm.
• Gauge: The conventional numbering system corresponding to a nominal thickness.
• Coil width: The width of uncut material supplied on a coil.
• Sheet weight: Calculated from area, thickness and material density.

Not every stock size is available in every material, gauge or finish; confirm actual availability with the supplier.

A gauge number alone does not establish a roof panel’s allowable span. Designers must check base-metal thickness, steel grade, roof panel profile, support spacing, wind uplift, snow loading, and the approved manufacturer span tables. See the Metal Roof Panel Span Chart for structural span capacity and the Roof Purlin Size Chart for supporting member dimensions.

Relevant design inputs include pressure class, duct dimensions, reinforcement, joint type, and applicable SMACNA requirements. There is no simplified gauge-by-duct-width chart that serves as a universal standard; consult the applicable SMACNA HVAC duct construction manual and the project’s specifications for actual selection.

Corrosion exposure, fabrication requirements, fastening, thermal expansion and manufacturer recommendations all affect the appropriate selection. There is no universal gauge recommendation for every flashing or gutter application; check the specific manufacturer’s instructions. See the Nail Size Chart for related fastener dimensions.

Bend Radius, Bend Allowance and Sheet Thickness

Inside bend radius, bend allowance, K-factor and flat-pattern dimensions all depend on the actual specified material thickness, not an assumed nominal gauge value. Using the true measured or ordered thickness in these calculations, rather than a rounded gauge equivalent, helps fabricators achieve accurate flat-pattern layouts.

1. Measure away from cut edges and burrs, which can distort readings.
2. Check several locations across the sheet.
3. Confirm the material before comparing to any chart.
4. Determine whether the measurement includes coating (galvanized, painted) or represents bare base metal.
5. Compare the measurement with the purchase specification where available.
6. Respect instrument accuracy and material tolerance ranges; do not over-interpret small variations.

An inexpensive gauge template may help identify approximate stock, but it cannot establish full compliance with a dimensional material specification.

1. Identify the material first (steel, stainless, aluminum, galvanized).
2. Measure the thickness with a micrometer or caliper.
3. If coated, determine whether the measurement includes zinc, paint, or another finish.
4. Consult the correct material-specific chart above.
5. Compare the result with the actual order specification if available.
6. Recognize that adjacent gauge values may fall within measurement or product-tolerance considerations rather than indicating a different nominal gauge.

1. Identify the intended application.
2. Determine the required metal and alloy.
3. Establish structural, stiffness, forming or corrosion requirements.
4. Identify the applicable material specification (ASTM A568, A653, A480, B209, etc.).
5. Select a nominal decimal or metric thickness.
6. Determine whether a gauge designation is appropriate for ordering.
7. Account for coating and dimensional tolerances.
8. Verify available stock sizes with the supplier.
9. Calculate sheet weight and required quantity.
10. Confirm the final specification with the supplier or approved design before ordering.