Convert between common PCB units: mil, mm, inch, μm and copper weight.
| From | To | Factor |
|---|---|---|
| 1 mil | mm | 0.0254 |
| 1 mm | mil | 39.3701 |
| 1 inch | mm | 25.4 |
| 1 mm | μm | 1000 |
| Weight (oz/ft²) | Thickness (μm) | Thickness (mil) |
|---|---|---|
| 0.5 oz | 17.5 μm | 0.69 mil |
| 1 oz | 35 μm | 1.37 mil |
| 2 oz | 70 μm | 2.76 mil |
| 3 oz | 105 μm | 4.13 mil |
A mil (also called thou) is 1/1000 of an inch, equal to 0.0254 mm. It's commonly used in PCB design for trace widths, spacing, and drill sizes.
1oz copper refers to the weight of copper per square foot, which equals approximately 35 μm (1.37 mil) thickness. This is the standard way to specify copper weight on PCBs.
PCB design uses both imperial (mil, inch) and metric (mm, μm) units. American datasheets typically use mil, while Asian manufacturers often use mm.