Convert Standard Wire Gauge (SWG) to millimeter (mm) diameter using standard reference values.
The SWG to mm Calculator is an essential online tool that allows you to quickly and accurately convert Standard Wire Gauge (SWG) sizes into millimeters (mm). Whether you’re working in manufacturing, electrical wiring, jewelry, or metalworking, knowing the precise diameter of a wire in mm is critical to ensuring proper fit, conductivity, and safety.
SWG, or Standard Wire Gauge, is a British imperial system still used in some parts of the world for measuring wire thickness. This tool makes it simple to translate these measurements into metric values for international compatibility and precision engineering.
Standard Wire Gauge (SWG) is a unit of measurement used primarily in the UK and former Commonwealth countries. It was originally defined in the 19th century and is based on the diameter of the wire rather than its cross-sectional area. Key characteristics of the SWG system include:
For example, SWG 10 is thicker than SWG 20. However, the scale is not linear, so direct conversion into mm can’t be done by estimation — it requires a conversion table or calculator.
With the widespread adoption of the metric system in manufacturing and engineering, many global specifications now require measurements in millimeters. Converting SWG to mm helps with:
| SWG | Diameter (mm) |
|---|---|
| 4 | 5.89 |
| 6 | 4.88 |
| 8 | 4.06 |
| 10 | 3.25 |
| 12 | 2.64 |
| 14 | 2.03 |
| 16 | 1.63 |
| 18 | 1.22 |
| 20 | 0.91 |
| 22 | 0.71 |
| 24 | 0.56 |
The calculator is fast, reliable, and eliminates the need to memorize conversion tables.
SWG and AWG (American Wire Gauge) are not the same. They follow different conversion paths, and the same number in each system does not represent the same diameter:
Using the wrong conversion could cause a mismatch in mechanical or electrical design. Always confirm your gauge system before using any datasheet or product specification.
A: Yes, SWG is often used to describe the thickness of metal sheets as well. This calculator works for both wires and sheets.
A: The calculator supports SWG 0 to SWG 50, covering standard wire and sheet sizes across applications.
A: While metric and AWG systems are more common, SWG is still used in specific industries in the UK, India, South Africa, and Australia.
A: Yes! You can use our mm to SWG calculator for reverse lookup.
Several standards reference SWG measurements in various applications:
The SWG to mm Calculator is more than a conversion tool — it’s a productivity booster and design accuracy aid. Whether you're designing PCBs, choosing sheet metal, wrapping coils, or selecting audio cables, getting the measurement right the first time is essential.
Don’t rely on outdated charts or manual math. Bookmark our SWG to mm calculator and make precise, fast, and global-ready decisions every time you wire, design, or fabricate!
One of the most overlooked but critical applications of SWG to mm conversion lies in electrical resistance analysis. The thinner the wire (higher SWG number), the more resistance it offers per meter. This affects how much current can safely pass through and how much voltage drop occurs over long distances.
Here’s an example using copper wire:
The difference may seem small, but in circuits carrying high current or over long cable runs, it can lead to overheating, energy loss, and performance issues.
By converting SWG to millimeters, you can then reference resistance charts or calculate real resistance using the formula:
R = (ρ × L) / A
This is especially important for electricians, robotics engineers, and hobbyists working on custom wiring systems.
In the jewelry industry, wire thickness affects aesthetics, durability, and ease of bending. SWG is widely used in countries like India and the UK for handmade jewelry wire.
Here’s how wire gauge translates for common jewelry needs:
Being able to convert these into millimeters helps jewelers choose the correct mandrels, drill sizes, or even metal pricing by weight (since thickness affects mass).
SWG is not limited to wire — it also applies to metal sheets. Sheet thickness impacts:
Here’s a short table showing sheet thickness in SWG vs mm:
| SWG | Sheet Thickness (mm) | Common Use |
|---|---|---|
| 16 | 1.63 mm | Body panels, enclosures |
| 18 | 1.22 mm | Air ducts, HVAC systems |
| 20 | 0.91 mm | Roof flashing, brackets |
| 24 | 0.56 mm | Crafts, decorative sheet |
By converting SWG to mm, manufacturers can program laser cutters, press brakes, and CNC machines with precision. Many CAD/CAM software platforms accept only metric input, making this calculator a must-have in metalworking workshops.
Choosing an incorrect SWG wire size — especially one that’s too thin — can be dangerous. A thinner wire heats up faster under load, increasing the risk of:
By using the SWG to mm calculator, you can determine the real-world wire diameter and reference national electrical codes (like the IEC or NEC) to verify safe ampacity.
If you’re purchasing materials from one country but building or exporting to another, wire gauge mismatches can cause serious production delays or safety issues. SWG is still used in the UK, India, Pakistan, and some African nations. However, international engineering documentation usually uses millimeters (mm) or square millimeters (mm²).
Being able to convert SWG to mm allows:
Even after conversion, wire sizes can vary slightly due to coating, manufacturing tolerance, or deformation. Always double-check actual diameter using a digital or vernier caliper for precision work.
For professionals in the field or factories with poor connectivity, having a printed SWG to mm chart can be helpful. We offer a downloadable PDF chart that lists all 50 SWG sizes with equivalent mm values and suggested use cases.
You can also screenshot the calculator result and paste it into your project documentation or production sheet.
Engineers working in power distribution, windings, or automotive systems often combine SWG wire sizing with formulas involving:
Accurate diameter in mm helps compute core areas, inductance, resistance, and EMI shielding factors with precision.
This makes the SWG to mm Calculator a versatile tool in almost every industry that works with metal, wire, or electrical systems.
Don’t waste time flipping through tables or risking miscalculations. Save and share this free calculator with colleagues, students, or teammates so everyone can stay on the same page — literally and figuratively!
📌 Pro Tip: Add this page to your browser’s bookmarks bar for one-click access every time you're wiring, fabricating, or specifying parts.
The SWG to mm Calculator is more than just a conversion tool. It’s your digital assistant in electrical engineering, fabrication, jewelry design, and procurement. It bridges imperial and metric systems, ensuring compatibility, accuracy, and efficiency in every project you undertake.
💡 Use it, share it, and build smarter — one wire at a time.