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PCB Unit Converter
Convert between common PCB units: mil, mm, inch, μm and copper weight.
Quick Reference
1 mil = 0.0254 mm
1 mm = 39.37 mil
1 inch = 25.4 mm
1 mm = 1000 μm
How to Use
- Select Length or Copper Weight conversion mode
- Enter a value in any input field
- All equivalent values are calculated automatically
- Click the copy icon to copy any value to clipboard
Conversion Reference
Length Units
| From | To | Factor |
|---|---|---|
| 1 mil | mm | 0.0254 |
| 1 mm | mil | 39.3701 |
| 1 inch | mm | 25.4 |
| 1 mm | μm | 1000 |
Copper Weight
| 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 |
Frequently Asked Questions
What is a mil in PCB design?
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.
What does 1oz copper mean?
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.
Why use different unit systems?
PCB design uses both imperial (mil, inch) and metric (mm, μm) units. American datasheets typically use mil, while Asian manufacturers often use mm.