Metal Panel Thickness: How to Specify Aluminum, Stainless Steel and Steel Panels

For aluminum panels, a safe starting range is 1.5 to 2 mm indoors, 2 to 3 mm on exteriors, and 3 to 4 mm once a panel gets large or heavily perforated.

Stainless steel starts thinner, because it’s stiffer. But the right metal panel thickness always depends on panel size, supports, finish and location, so treat any range as a starting point for the engineer, and not as a final answer.

Most specification problems aren’t about picking the wrong number. They come from writing the number in the wrong unit, or from comparing two quotes that quietly use different thicknesses.

This guide covers how to state metal panel thickness correctly, what panels weigh at each size, why a thicker panel is stiffer by far more than you’d expect, where composite panels fit in, and where thickness stops helping. Every figure is calculated, and the sources are linked.

Quick Answer: Typical Metal Panel Thickness by Use

The table gives common starting ranges. It isn’t a design calculation, and structural fixing spacing and wind loads still need an engineer.

The aluminum ranges match the thickness table in our perforated aluminum panels guide. The stainless ranges are typical workshop practice, not a code requirement, so confirm them against your load case.

Why Gauge Is the Wrong Unit for Metal Panel Thickness

Gauge numbers feel precise but they aren’t. A gauge isn’t a unit, it’s a legacy numbering system, and the same number gives a different thickness for each metal. ASTM A480 discourages gauge for exactly this reason, and ATAS advises specifying the base-metal thickness rather than a gauge.

The figures below come from a published gauge chart. Look at how far apart the same gauge number lands.

Here’s what that means in practice. A 16 gauge aluminum sheet is 1.29 mm, which is 15.1% thinner than 16 gauge steel at 1.519 mm. At 12 gauge the gap grows to 22.8%. Order “16 gauge” expecting 1.5 mm and you could receive a sheet 14% thinner than you assumed.

Write millimetres, name the metal, and say whether you mean base metal or coated metal. Nobody can argue with “2.0 mm aluminum 5052-H32, base metal.”

What a Metal Panel Thickness Line Should Contain

A usable metal panel thickness line states the metal and alloy or grade, the temper where relevant, the nominal base-metal thickness in millimetres, and the tolerance.

ATAS notes that tolerances are normally split evenly above and below nominal, so a 2.0 mm panel can legitimately measure slightly under 2.0 mm. Ask for the tolerance in writing.

How Metal Panel Thickness Changes Weight

Metal panel thickness decides weight, and weight decides your subframe, your fixings and your lifting plan. The table uses densities of 2.70 g/cm³ for aluminum, 7.86 for 304 stainless and 7.85 for carbon steel, in line with published property tables.

Take a 100 m² façade. In 2 mm aluminum it carries 540 kg of metal. Move to 3 mm and it’s 810 kg, which is 50% more. In 2 mm stainless the same area weighs 1,572 kg, nearly three times the 2 mm aluminum. That difference reaches the structure.

Why a Slightly Thicker Panel Is Much Stiffer

Bending stiffness of a flat panel scales with the cube of its thickness. Double it and the panel is eight times stiffer, while the weight only doubles.

For a given span and load, the deflection follows the same rule. It scales with 1 ÷ (E × t³), where E is the modulus of elasticity. The numbers below use 69 GPa for aluminum, which matches the 68.9 GPa listed for 6061 in the property table above, and 193 GPa for 304 stainless.

• Aluminum from 2 mm to 3 mm: stiffness rises 3.4 times (3³ ÷ 2³ = 3.375), so deflection falls by about 70%.
• Stainless from 1.5 mm to 2 mm: stiffness rises 2.4 times, so deflection falls by about 58%.
• Aluminum 3 mm against stainless 1.5 mm: the aluminum is 2.9 times stiffer, and it weighs 8.10 kg/m² against 11.79 kg/m².

So a step of just 0.5 mm often does more for flatness than any change of metal or finish.

And when weight is fixed, aluminum wins on stiffness. A stainless panel of 1.5 mm weighs 11.79 kg/m². An aluminum panel of the same weight would be 4.37 mm thick and roughly 8.8 times stiffer in bending.

Stiffness isn’t everything, though. Stainless is harder and resists dents and scratches better. Aluminum is lighter but softer. We’d choose between them on finish, weight limit and abuse expected, not on stiffness alone.

Thickness by Material: Aluminum, Stainless and Steel

Aluminum

Aluminum is the usual choice when weight matters or the panel is large, and its metal panel thickness is usually the first number to settle.

Alloy matters as much as thickness. For exteriors near the sea, 5052 is a common pick: published data lists it at about 2.68 g/cm³ and 70 GPa, so it behaves like the numbers above.

Ask for the alloy, the temper and the mill certificate along with the thickness.

For larger panels, don’t jump straight to a thicker sheet. Folded edges, returns and stiffening ribs can add more rigidity than another millimetre of flat sheet. Our metal wall panel guide covers how panel construction affects the result.

Stainless Steel

Stainless gets away with a lower metal panel thickness because of its modulus and hardness. The catch is cost and weight, plus the finish.

Mirror and PVD surfaces show every dent and every ripple, so a thin mirror panel that looks fine on the drawing can look poor on site. Read the grade comparison in our 304 vs 316 stainless guide and the finish notes in PVD finishing before you fix the thickness.

Carbon Steel, Galvanized Steel and Corten

These weigh the same as stainless per mm. Galvanized sheet has its own gauge scale, so always quote it in millimetres. For weathering steel, read the Corten steel guide because the surface treatment and the way the patina forms affect how thick you’d specify.

Composite Panels: Why 4 mm Isn’t 4 mm of Aluminum

Search for panel thickness and aluminum composite panels (ACP) show up constantly. Their quoted thickness is the whole sandwich, two thin aluminum skins around a core. A 4 mm composite panel isn’t a 4 mm aluminum sheet.

The numbers below compare solid aluminum, calculated from E = 69 GPa, with the published data for Alucobond Plus, which has 0.5 mm skins and a mineral-filled core.

A 4 mm composite weighs slightly less than 3 mm solid aluminum and is about 1.5 times as rigid. A 3 mm composite weighs about the same as 2 mm solid and is roughly 2.7 times as rigid.

That’s why composite looks so efficient for large flat façade panels. The skins sit far from the middle of the section, where they do most of the work.

Solid sheet still wins when the design needs deep folds, welded corners or heavy perforation, because a composite is a flat laminated product. These figures come from one manufacturer, so check the data sheet of the product you’re actually quoting.

What Thickness Can and Can’t Fix: Oil Canning

Oil canning is the visible waviness or pillowing on a flat metal surface. An industry bulletin citing ASTM E1514 and the Metal Construction Association treats it as an appearance matter, not a structural one, and notes that manufacturers can’t promise it’ll never appear.

Metal panel thickness helps, but it’s one lever among several. The same bulletin lists these as the others:

• narrower panel widths
• stiffeners or ribs
• a flatter substrate
• sliding clips or slotted holes, with fasteners at the right tightness
• lower-gloss finishes, since high gloss shows waviness more

So if a panel oil-cans, look at the fixing and the substrate before you add thickness. Thickness gets blamed because it’s the number on the drawing.

Panel Size, Perforation and Thickness

A large panel needs a greater metal panel thickness than a small one with the same pattern. Perforation removes metal, so holes weaken the sheet.

A guide to keep: the hole diameter should be at least as big as the sheet thickness when punching, and laser-cut bridges should be at least as wide as the thickness, more on big outdoor panels. The full open-area and hole-size table is in our perforated aluminum guide so we won’t repeat it here.

Cutting method matters too. Laser cutting puts heat into thin sheet, so very thin panels with dense patterns can distort. Shaped panels add spring-back and heat sensitivity, which the wave pattern panel guide discusses.

Thermal Movement: Thickness Doesn’t Fix It

A thicker panel moves just as much. Use 23 µm/m·°C for aluminum and 17 for stainless, from the same property table. A 3 m panel with a 60 °C temperature swing grows about 4.1 mm in aluminum and 3.1 mm in stainless.

The panel isn’t stopped by being thick. It needs room to move, with slotted holes and floating fixings.

Thick panels that are rigidly fixed can overstress their fixings instead of oil-canning, which is worse. This is why thickness and fixing design are one decision, not two.

Metal Panel Thickness in Saudi Arabia

Temperatures swing widely between a winter night and a summer afternoon in much of the Kingdom, and sunlit dark finishes run hotter than the air. That raises thermal movement, so allow for it in the fixing design.

Inland cities such as Riyadh typically see wider day-to-night swings than the coast. Coastal sites such as Jeddah, Dammam and Jubail add salt, which affects alloy and grade more than thickness. Our exterior façade design guide and the metal cladding overview cover site conditions.

Public areas change the answer too. Lift cars and airport concourses take knocks from trolleys and luggage. For these we’d move up a size. See our notes on elevator cladding for how that plays out.

Wind load on tall buildings is a structural question, so metal panel thickness is never set from a table alone. Your façade engineer sets it under the Saudi Building Code, where SBC 301 covers structural loads, and the panel thickness follows from that, not from this guide.

Worked Example: A Lift Lobby Wall

Say a lobby wall uses panels of 1,200 × 2,400 mm, an area of 2.88 m² each. Two installers will lift them, and the wall is touched all day. Here’s how the options compare.

On a lift lobby wall, the stainless options feel solid and resist dents, but at 34 to 45 kg a panel they need lifting aids and a stronger subframe. The 3 mm aluminum panel is stiffest per kilogram. Which one wins depends on the finish, the budget and who handles the panel on site.

That’s the point of running numbers before you pick. The cheapest metal panel thickness on paper often costs more once handling and subframe are counted.

Thickness, Dents and Impact

Metal panel thickness also governs how a panel takes knocks. ATAS cites the Metal Construction Association and a US Steel formula to say a 10% change in thickness can alter impact resistance by as much as 150%.

Treat that as the upper end of a range, not a promise, because panel construction and support spacing change the result.

The practical lesson holds either way. In public or high-touch areas, small increases in thickness buy a real improvement in dent resistance, and that matters more on mirror and PVD finishes.

How to Check Metal Panel Thickness on Delivery

Don’t wait for a complaint to check metal panel thickness. Measure when the pallets arrive.

Use a micrometre or a caliper on a cut edge, and measure the base metal where there’s no coating. Take readings in several places on several panels, because tolerance is allowed above and below nominal. Compare the average and the extremes with the figure and tolerance in your order.

If the readings fall outside the stated tolerance, photograph the panel, note the batch and raise it before fabrication or installation starts. Rejecting panels later is far harder. Keep the mill certificate with the delivery record too, since it connects the sheet to its alloy and temper.

How to Compare Two Quotes Fairly

A supplier quoting 15% less per square metre may simply be quoting a lower metal panel thickness. Before comparing, put both on the same basis.

Take two quotes for 100 m² of aluminum. One is for 2 mm and one for 3 mm. The second contains 270 kg more metal (810 minus 540).

If the price per m² is close, the 3 mm quote is the better value on metal content alone. If the thinner quote is much lower, find out whether the difference is just thickness.

Use this checklist when you compare:

1. Same metal, alloy and temper
2. Same nominal thickness in mm, base metal
3. Same tolerance
4. Same finish and coating system
5. Same panel size and stiffening
6. Same fixings and delivery terms

Our metalwork mistakes guide lists more of the traps that make quotes look alike when they aren’t.

Common Mistakes When Specifying Thickness

• Specifying metal panel thickness in gauge without naming the metal.
• Ignoring tolerance, then rejecting a panel that’s within it.
• Assuming thicker always means better. A thick panel on a rigid fixing still cracks.
• Fixing the number before the panel size and support spacing are known.
• Choosing a thin sheet for a mirror or PVD finish in a high-traffic area.
• Comparing quotes without checking the thickness in each.
• Forgetting the extra weight on the subframe when going up a size.

FAQ About Metal Panel Thickness

What is the standard metal panel thickness?

There isn’t one standard metal panel thickness. Aluminum façade panels are commonly 2 to 3 mm, and interior wall panels run thinner. Stainless cladding often sits between 1.0 and 2.0 mm. Always specify the actual millimetres for your project.

Is 2 mm aluminum thick enough for an exterior façade?

Often, for modest panel sizes with supports close together. Larger panels, higher wind zones and heavy perforation push the answer toward 3 mm or toward adding stiffeners. Your façade engineer decides.

What is the difference between gauge and millimetres?

Millimetres are a measured unit. Gauge is a numbering system whose meaning changes by metal. 16 gauge aluminum is 1.29 mm while 16 gauge steel is 1.519 mm.

How much does aluminum panel weigh per square metre?

Multiply thickness in mm by 2.7. A 2 mm panel weighs 5.4 kg/m², and 3 mm weighs 8.1 kg/m².

Is a thicker panel always better?

No. A thicker metal panel adds stiffness and weight, but the fixing method, panel width and stiffeners often matter more for flatness. Thicker panels also cost more and load the structure.

Does thickness include the coating?

Specify base-metal thickness and treat the coating as extra. ATAS advises stating it that way so the number can be checked.

How much thinner can stainless be than aluminum?

For equal bending stiffness, stainless can be about 29% thinner, because (69 ÷ 193)^(1/3) is 0.71. A 3 mm aluminum panel matches a stainless panel of roughly 2.1 mm, but that stainless panel weighs about 16.7 kg/m² against 8.1. It’s thinner, not lighter.

Is a 4 mm composite panel the same as 4 mm aluminum?

No. A composite panel’s thickness includes the core. In the Alucobond Plus data, a 4 mm panel has 0.5 mm aluminum skins and weighs 7.6 kg/m², against 10.8 kg/m² for a solid 4 mm aluminum sheet.

What should I put in an RFQ for metal panels?

Metal and alloy, nominal base thickness and tolerance, panel sizes, finish, quantity, fixing type and delivery site. The more precise it is, the easier it is to compare quotes.

Conclusion: Specify the Panel, Not Just the Number

Write metal panel thickness in millimetres, name the metal, state the tolerance, and decide it together with panel size and fixing. A step of half a millimetre changes stiffness far more than weight, and no thickness removes the need to allow for movement.

If you’re planning a project, Rounuq Almsar can review panel size, material and finish against your site. See the metal cladding and metal wall panel pages for the systems we fabricate, or contact us with your drawings and quantities.