PCB Unit Converter
Convert between mil, mm, \u00b5m, and inch for PCB dimensions. Convert copper weight (oz/ft\u00b2) to thickness (\u00b5m / mil).
PCB Length Converter
Trace width, spacing, drill, board dimensions
mm0.12700
µm (micron)127.00
inch5.000e-3
1 mil = 0.0254 mm = 25.4 \u00b5m | 1 mm = 39.37 mil = 1000 \u00b5m
Copper Weight Converter
Copper foil thickness: oz/ft\u00b2 \u2194 \u00b5m \u2194 mil
µm35.000
mil1.3780
1 oz/ft\u00b2 = 35 \u00b5m = 1.378 mil | \u00bd oz = 17.5 \u00b5m | 2 oz = 70 \u00b5m
Copper Weight Quick Reference
| Copper Weight | Thickness (\u00b5m) | Thickness (mil) | Typical Use |
|---|---|---|---|
| 0.5 oz | 17.5 µm | 0.69 mil | Inner layer fine pitch, HDI |
| 1 oz | 35 µm | 1.38 mil | Standard outer layer, most PCBs |
| 2 oz | 70 µm | 2.76 mil | Power traces, high current |
| 3 oz | 105 µm | 4.13 mil | Heavy copper, bus bars |
| 4 oz | 140 µm | 5.51 mil | Very heavy copper, power distribution |
Common PCB Trace Widths
| mil | mm | Typical Use |
|---|---|---|
| 3 mil | 0.076 mm | Fine pitch, HDI, min trace/space |
| 4 mil | 0.102 mm | Standard minimum width (JLCPCB 1oz) |
| 5 mil | 0.127 mm | General signal traces |
| 6 mil | 0.152 mm | Standard signal routing |
| 8 mil | 0.203 mm | Power traces |
| 10 mil | 0.254 mm | Power, ground planes |
| 12 mil | 0.305 mm | High current traces |
| 20 mil | 0.508 mm | Very high current |
How copper weight works
PCB copper thickness is specified in ounces per square foot (oz/ft\u00b2), a legacy unit from the plating industry. The number represents the thickness of copper if 1 oz of copper were rolled flat over exactly 1 ft\u00b2 of area. The industry-standard conversion is 1 oz/ft\u00b2 = 35 \u00b5m = 1.378 mil. Most standard 2-layer and 4-layer PCBs use 1 oz copper (35 \u00b5m) on outer layers and 0.5 oz (17.5 \u00b5m) on inner layers. Heavy copper boards (2-4 oz) are used for power distribution and high-current applications.