mm to AWG Converter
Convert millimeter diameter to American Wire Gauge with precision matching, comprehensive specifications, and professional electrical engineering data
Formula: AWG = -39 × log₁₀(mm) + 36
This calculator converts wire diameter in millimeters to the equivalent American Wire Gauge (AWG) size.
Complete mm to AWG Conversion Reference
Detailed diameter to wire gauge conversion with electrical specifications, resistance values, and typical applications
| Diameter (mm) | AWG Size | Area (mm²) | Resistance (Ω/km) | Ampacity (A) | Typical Applications |
|---|---|---|---|---|---|
| 0.25 | 30 | 0.051 | 103.2 | 0.5 | Magnet wire, fine electronics, precision instruments |
| 0.32 | 28 | 0.081 | 64.9 | 0.8 | Thermocouple wire, instrumentation, sensor cables |
| 0.4 | 26 | 0.129 | 40.8 | 1 | Computer cables, telephone wire, data transmission |
| 0.51 | 24 | 0.205 | 25.7 | 1.5 | Signal cables, low power electronics, control circuits |
| 0.64 | 22 | 0.326 | 16.1 | 2.5 | Control circuits, alarm systems, communication |
| 0.81 | 20 | 0.518 | 10.2 | 4 | Lighting circuits, control panels, low voltage |
| 1.02 | 18 | 0.823 | 6.39 | 7 | Appliance cords, fixture wiring, extension cords |
| 1.29 | 16 | 1.31 | 4.02 | 10 | Extension cords, outlet circuits, small appliances |
| 1.63 | 14 | 2.08 | 2.53 | 15 | Branch circuits, outlets, lighting, general wiring |
| 2.05 | 12 | 3.31 | 1.59 | 20 | Kitchen circuits, bathroom outlets, air conditioning |
| 2.59 | 10 | 5.26 | 1 | 30 | Electric dryers, ranges, large appliances |
| 3.26 | 8 | 8.37 | 0.628 | 40 | Sub-panels, large appliances, electric water heaters |
| 4.12 | 6 | 13.3 | 0.395 | 55 | Service entrance, feeders, sub-panel connections |
| 5.19 | 4 | 21.2 | 0.248 | 70 | Service entrance, sub-panels, large load feeders |
| 5.83 | 3 | 26.7 | 0.197 | 85 | Service entrance, industrial feeders, large motors |
| 6.54 | 2 | 33.6 | 0.156 | 95 | Service entrance, large industrial loads, feeders |
| 7.35 | 1 | 42.4 | 0.124 | 110 | Service entrance, industrial applications, large feeders |
| 8.25 | 1/0 | 53.5 | 0.098 | 125 | Service entrance, industrial feeders, large installations |
| 9.27 | 2/0 | 67.4 | 0.078 | 145 | Service entrance, industrial applications, main feeders |
| 10.4 | 3/0 | 85 | 0.062 | 165 | Service entrance, industrial feeders, large facilities |
| 11.68 | 4/0 | 107.2 | 0.049 | 195 | Service entrance, industrial feeders, major installations |
Understanding the mm to AWG Conversion
Converting a wire's diameter in millimeters (mm) to an American Wire Gauge (AWG) value involves a reverse logarithmic formula. The calculator finds the AWG number 'n' that corresponds to a given diameter 'd'.
n = -39 * log₁₀(d / 0.127) + 36
Logarithmic Nature: Because the AWG scale is logarithmic, a small change in millimeters can result in a significant jump in AWG size, especially for smaller diameter wires.
Nearest Standard Size: Real-world wires are manufactured in standard AWG sizes. It is rare for a measured millimeter diameter to convert perfectly to a standard gauge. Our calculator provides the calculated AWG value and also identifies the closest standard manufactured AWG size, helping you select the correct real-world product.
Why Round Up?: When a diameter falls between two standard AWG sizes, it is often a best practice in electrical engineering to select the lower AWG number (which is a thicker wire). This ensures a higher safety margin for current capacity and reduces voltage drop.
Application and Selection Guide
When you have a diameter in mm, here's how to choose the right AWG wire for your project.
Identify Current Load (Amps)
The most critical factor is the amount of current the wire needs to carry. Check the ampacity rating for the closest standard AWG size. Ensure the wire's ampacity is greater than the maximum current of your circuit, applying any necessary derating for temperature or bundling.
Consider the Physical Constraints
Your measured diameter might be for a bare conductor. The final AWG wire will have insulation, increasing its overall diameter. Ensure the selected wire will fit within conduits, terminals, and any other physical constraints of your installation.
Match Material and Type
Ensure the wire material (e.g., copper, aluminum) and type (solid vs. stranded) match your requirements. Stranded wire is more flexible for the same AWG, while solid wire is more rigid. Aluminum wire must be a larger gauge than copper to carry the same current safely.
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