Sheet Metal Thickness Gauge Charts: A No-Nonsense Guide for Engineers
Let’s clear something up: a “16-gauge” sheet doesn’t mean the same thing for aluminium as it does for steel. And no, gauge isn’t a unit—it’s a legacy system wrapped in confusion.
In this guide, we’ll break down how gauge charts work, what thickness means across materials, and how to avoid painful manufacturing surprises. Whether you’re designing HVAC ducts or automotive brackets, knowing your gauges matters.
What Is a Sheet Metal Gauge Chart?
A sheet metal gauge chart shows the thickness of a metal sheet based on its gauge number. But here’s the catch: gauges aren’t linear, and they’re not the same for every material.
A gauge chart translates “gauge” into measurable values, typically in inches or millimetres. In this case, we focus entirely on millimetres. It’s your go-to reference when choosing material thickness for design and manufacturing.
Gauge ≠ Thickness: Why It’s Confusing
Gauge started as a manufacturing shorthand in the 19th century. The smaller the number, the thicker the sheet—sort of.
To make things worse, the same gauge number refers to different thicknesses across materials:
16 gauge steel ≠ 16 gauge aluminium
Galvanised steel has its scale
Stainless steel adds yet another variation
So yes, gauge can be dangerously misleading. Always check the chart.
Two Systems You Might See: AWG and SWG
While not always used for sheet metal, gauge systems like Birmingham Wire Gauge (BWG), also known as Standard Wire Gauge (SWG), remain widely referenced across materials like steel, aluminum, and zinc.
In this guide, all gauge-to-thickness conversions follow the BWG system. We do not use American Wire Gauge (AWG), which is more common for wires than sheet metal.
Full Sheet Metal Gauge Charts in Millimetres
We’ve created dedicated tables for the most common sheet metal materials, each showing gauge numbers alongside thickness values in millimetres.
Available materials:
- Standard steel
- Galvanized steel
- Stainless steel
- Carbon steel
- Aluminium
- Brass
- Copper
- Zinc
Each table adheres to the Birmingham Wire Gauge (BWG) system and reflects actual sourcing data. Use these charts during part design, procurement, or quality checks to avoid miscommunication and mismatched specs.
Keep in mind: actual thickness may vary slightly by supplier, standard, or fabrication method. Always confirm final specs with your manufacturer.
Standard Steel Gauge Chart (Metric)
This table shows the thickness of standard (mild) steel in millimeters for each gauge number, based on verified data.
| Gauge | Standard Steel (mm) |
|---|---|
| 3 | 6.073 |
| 4 | 5.695 |
| 5 | 5.314 |
| 6 | 4.935 |
| 7 | 4.554 |
| 8 | 4.176 |
| 9 | 3.797 |
| 10 | 3.416 |
| 11 | 3.038 |
| 12 | 2.657 |
| 13 | 2.278 |
| 14 | 1.897 |
| 15 | 1.709 |
| 16 | 1.519 |
| 17 | 1.367 |
| 18 | 1.214 |
| 19 | 1.062 |
| 20 | 0.912 |
| 21 | 0.836 |
| 22 | 0.759 |
| 23 | 0.683 |
| 24 | 0.607 |
| 25 | 0.531 |
| 26 | 0.455 |
| 27 | 0.417 |
| 28 | 0.378 |
| 29 | 0.343 |
| 30 | 0.305 |
| 31 | 0.267 |
| 32 | 0.246 |
| 33 | 0.229 |
| 34 | 0.208 |
| 35 | 0.191 |
| 36 | 0.170 |
| 37 | 0.163 |
| 38 | 0.152 |
Galvanized Steel Gauge Chart (Metric)
This table lists the thickness of galvanized steel sheets in millimeters for each applicable gauge size. Only verified values are shown.
| Gauge | Galvanized Steel (mm) |
|---|---|
| 8 | 4.270 |
| 9 | 3.891 |
| 10 | 3.510 |
| 11 | 3.132 |
| 12 | 2.753 |
| 13 | 2.372 |
| 14 | 1.994 |
| 15 | 1.803 |
| 16 | 1.613 |
| 17 | 1.461 |
| 18 | 1.311 |
| 19 | 1.158 |
| 20 | 1.006 |
| 21 | 0.930 |
| 22 | 0.853 |
| 23 | 0.777 |
| 24 | 0.701 |
| 25 | 0.627 |
| 26 | 0.551 |
| 27 | 0.513 |
| 28 | 0.475 |
| 29 | 0.437 |
| 30 | 0.399 |
| 31 | 0.361 |
| 32 | 0.340 |
Stainless Steel Gauge Chart (Metric)
This table shows the thickness of stainless steel sheets in millimeters for common gauge sizes. Values are based on the Birmingham Wire Gauge (BWG) system.
| Gauge | Stainless Steel (mm) |
|---|---|
| 0000000 | 12.700 |
| 000000 | 11.902 |
| 00000 | 11.113 |
| 0000 | 10.320 |
| 000 | 9.525 |
| 00 | 8.733 |
| 0 | 7.938 |
| 1 | 7.145 |
| 2 | 6.746 |
| 3 | 6.350 |
| 4 | 5.954 |
| 5 | 5.555 |
| 6 | 5.159 |
| 7 | 4.763 |
| 8 | 4.366 |
| 9 | 3.967 |
| 10 | 3.571 |
| 11 | 3.175 |
| 12 | 2.779 |
| 13 | 2.380 |
| 14 | 1.984 |
| 15 | 1.786 |
| 16 | 1.588 |
| 17 | 1.427 |
| 18 | 1.270 |
| 19 | 1.110 |
| 20 | 0.953 |
| 21 | 0.874 |
| 22 | 0.792 |
| 23 | 0.714 |
| 24 | 0.635 |
| 25 | 0.556 |
| 26 | 0.475 |
| 27 | 0.437 |
| 28 | 0.396 |
| 29 | 0.358 |
| 30 | 0.318 |
| 31 | 0.277 |
| 32 | 0.259 |
| 33 | 0.239 |
| 34 | 0.218 |
| 35 | 0.198 |
| 36 | 0.178 |
| 37 | 0.168 |
| 38 | 0.157 |
Carbon Steel Gauge Chart (Metric)
This table lists the thickness of carbon steel sheet in millimeters for commonly used gauge numbers. Data sourced from Xometry.
| Gauge | Carbon Steel (mm) |
|---|---|
| 3 | 6.07 |
| 4 | 5.69 |
| 5 | 5.31 |
| 6 | 4.94 |
| 7 | 4.55 |
| 8 | 4.18 |
| 9 | 3.80 |
| 10 | 3.42 |
| 11 | 3.04 |
| 12 | 2.66 |
| 13 | 2.28 |
| 14 | 1.90 |
| 15 | 1.71 |
| 16 | 1.52 |
| 17 | 1.37 |
| 18 | 1.21 |
| 19 | 1.06 |
| 20 | 0.91 |
| 21 | 0.84 |
| 22 | 0.76 |
| 23 | 0.68 |
| 24 | 0.61 |
| 25 | 0.53 |
| 26 | 0.45 |
| 27 | 0.42 |
| 28 | 0.38 |
| 29 | 0.34 |
| 30 | 0.30 |
Aluminum Gauge Chart (Metric)
This table shows the thickness of aluminum sheet in millimeters for standard gauge numbers, based on the BWG system.
| Gauge | Aluminum (mm) |
|---|---|
| 000 | 12.700 |
| 00 | 11.308 |
| 0 | 10.069 |
| 1 | 8.971 |
| 2 | 7.993 |
| 3 | 5.827 |
| 4 | 5.189 |
| 5 | 4.620 |
| 6 | 4.115 |
| 7 | 3.665 |
| 8 | 3.264 |
| 9 | 2.906 |
| 10 | 2.588 |
| 11 | 2.304 |
| 12 | 2.052 |
| 13 | 1.829 |
| 14 | 1.628 |
| 15 | 1.450 |
| 16 | 1.290 |
| 17 | 1.151 |
| 18 | 1.024 |
| 19 | 0.912 |
| 20 | 0.813 |
| 21 | 0.724 |
| 22 | 0.643 |
| 23 | 0.574 |
| 24 | 0.511 |
| 25 | 0.455 |
| 26 | 0.404 |
| 27 | 0.361 |
| 28 | 0.320 |
| 29 | 0.287 |
| 30 | 0.254 |
| 31 | 0.226 |
| 32 | 0.203 |
| 33 | 0.180 |
| 34 | 0.160 |
| 35 | 0.142 |
| 36 | 0.127 |
| 37 | 0.114 |
| 38 | 0.102 |
| 39 | 0.089 |
| 40 | 0.079 |
| 41 | 0.086 |
| 42 | 0.076 |
| 43 | 0.069 |
| 44 | 0.061 |
| 45 | 0.053 |
| 46 | 0.048 |
| 47 | 0.043 |
| 48 | 0.041 |
| 49 | 0.033 |
| 50 | 0.030 |
| 51 | 0.027 |
| 52 | 0.024 |
Brass Gauge Chart (Metric)
This table shows the thickness of brass sheet in millimeters for selected gauge numbers, based on commonly used commercial standards.
| Gauge | Brass (mm) |
|---|---|
| 7 | 3.665 |
| 8 | 3.264 |
| 9 | 2.906 |
| 10 | 2.588 |
| 11 | 2.305 |
| 12 | 2.053 |
| 14 | 1.628 |
| 16 | 1.291 |
| 18 | 1.024 |
| 20 | 0.812 |
| 22 | 0.644 |
| 24 | 0.511 |
| 26 | 0.405 |
| 28 | 0.321 |
| 30 | 0.255 |
Copper Gauge Chart (Metric)
This table shows the thickness of copper sheet in millimeters for selected gauge numbers. Values reflect typical standards used in fabrication and HVAC industries.
| Gauge | Copper (mm) |
|---|---|
| 7 | 4.572 |
| 8 | 4.191 |
| 9 | 3.759 |
| 10 | 3.404 |
| 11 | 3.048 |
| 12 | 2.769 |
| 14 | 2.108 |
| 16 | 1.651 |
| 18 | 1.245 |
| 20 | 0.889 |
| 22 | 0.711 |
| 24 | 0.559 |
| 26 | 0.457 |
| 28 | 0.356 |
| 30 | 0.305 |
Zinc Gauge Chart (Metric)
This table displays the sheet thickness of zinc in millimeters for available gauge numbers, based on verified reference data.
| Gauge | Zinc (mm) |
|---|---|
| 1 | 0.051 |
| 2 | 0.102 |
| 3 | 0.152 |
| 4 | 0.203 |
| 5 | 0.254 |
| 6 | 0.305 |
| 7 | 0.356 |
| 8 | 0.406 |
| 9 | 0.457 |
| 10 | 0.508 |
| 11 | 0.610 |
| 12 | 0.711 |
| 13 | 0.813 |
| 14 | 0.914 |
| 15 | 1.016 |
| 16 | 1.143 |
| 17 | 1.270 |
| 18 | 1.397 |
| 19 | 1.524 |
| 20 | 1.778 |
| 21 | 2.032 |
| 22 | 2.286 |
| 23 | 2.540 |
| 24 | 3.175 |
| 25 | 6.350 |
| 26 | 9.525 |
| 27 | 12.700 |
| 28 | 25.400 |
Why Tolerances Matter More Than You Think
Let’s say you spec a sheet with a tolerance of ±0.1 mm. Then your finish adds 0.05 mm. Suddenly, you’re out of spec.
Every process, cutting, bending, coating, affects your result. And every gauge has its tolerance range. That’s why professional manufacturers always work from both nominal thickness and tolerance.
Need help with tight specs? MakerVerse supports specific ISO requirements and custom tolerance settings.
Choosing the Right Gauge for Your Application
Automotive
18–22 gauge for body panels
10–14 gauge for structural brackets
HVAC
26 gauge for ductwork
18–20 gauge for plenums
Enclosures
14–18 gauge for sheet metal cabinets
16–20 gauge for electrical boxes
Not sure what to choose? Upload your design and we’ll help you get it made.
Common Mistakes (and How to Avoid Them)
Using gauge without a material type
→ Always specify the material + thickness.Relying only on gauge in drawings
→ Include millimetre thickness directly.Forgetting post-processing effects
→ Add or subtract thickness for anodizing, painting, or plating.
FAQs About Sheet Metal Gauges
Q: Is 16 gauge always the same thickness?
No. Steel, aluminium, and stainless all have different thicknesses for the same gauge.
Q: What’s the best way to communicate sheet thickness?
Use millimeters and note the gauge as a reference only.
Q: Do gauge charts follow international standards?
Not always. Confirm the system with your supplier, especially for global sourcing.
Final Thoughts: From Design to Production
Gauge charts are helpful, but they’re not gospel. Always double-check material standards, communicate thickness in precise units, and account for real-world tolerances.
At MakerVerse, we help engineers go from spec to part, across sheet metal, CNC machining, and 3D printing. No guesswork. No supplier chase.
