PCB Copper Weight Reference

Copper weight (oz/ft²) to thickness conversion table with current carrying capacity for PCB trace design.

Conversion Formula

Weight to Thickness

1 oz/ft² = 35 μm = 1.37795 mil

General Formula

thickness (μm) = weight (oz) × 35

Copper Weight Specifications

Weight	Thickness (μm)	Thickness (mil)	Thickness (mm)	Current @ 1mm*
0.5 oz/ft²	17.5	0.689	0.0175	1.2 A
1 oz/ft²	35	1.378	0.0350	2 A
2 oz/ft²	70	2.756	0.0700	3.5 A
3 oz/ft²	105	4.134	0.1050	4.8 A
4 oz/ft²	140	5.512	0.1400	6 A
6 oz/ft²	210	8.268	0.2100	8.2 A

* Current capacity for 1mm trace width, external layer, 10°C temperature rise (IPC-2221)

Current Carrying Capacity (IPC-2221)

External layer, 10°C temperature rise above ambient. Internal layers carry approximately 50% of these values.

Copper Weight	1mm Trace	2mm Trace	3mm Trace
0.5 oz/ft²	1.2 A	1.9 A	2.5 A
1 oz/ft²	2 A	3.2 A	4.2 A
2 oz/ft²	3.5 A	5.6 A	7.4 A
3 oz/ft²	4.8 A	7.7 A	10.2 A
4 oz/ft²	6 A	9.6 A	12.7 A
6 oz/ft²	8.2 A	13.1 A	17.4 A

Applications by Copper Weight

0.5 oz/ft²(17.5 μm / 0.69 mil)

→Fine-pitch BGA routing
→High-density interconnect (HDI) boards
→Smartphone and tablet PCBs
→Inner layers in multilayer boards

Half-ounce copper is standard for HDI and fine-pitch designs. Lower current capacity limits use in power applications. Often paired with 1 oz outer layers.

1 oz/ft²(35 μm / 1.38 mil)

→General-purpose digital circuits
→Consumer electronics
→Signal routing layers
→Standard commercial PCBs

Most common copper weight for general PCB fabrication. Good balance of current capacity, cost, and manufacturability. Standard baseline for IPC-2221 calculations.

2 oz/ft²(70 μm / 2.76 mil)

→Power distribution layers
→Motor drivers
→LED lighting boards
→Automotive electronics
→Industrial control systems

Double the current capacity of 1 oz copper. Common choice for power planes and high-current traces. Increases board cost by ~20-30%. May require adjusted trace/space rules.

3 oz/ft²(105 μm / 4.13 mil)

→High-power DC-DC converters
→Battery management systems (BMS)
→EV/HEV power electronics
→Welding equipment

Heavy copper for demanding power applications. Requires special fabrication capabilities. Minimum trace/space typically 8-10 mil. Often combined with thinner signal layers.

4 oz/ft²(140 μm / 5.51 mil)

→Power supply boards
→Busbar replacement
→High-current motor controllers
→Renewable energy inverters

Heavy copper requiring specialty PCB fabrication. Not all fabs support 4 oz+. Expect longer lead times and higher costs. May need edge plating for thermal relief.

6 oz/ft²(210 μm / 8.27 mil)

→Extreme power applications
→Planar transformers
→High-current busbars on PCB
→Power conversion equipment

Ultra-heavy copper for extreme power requirements. Very few fabs can process 6 oz+. Often used with embedded busbars or coin insertion for thermal management.

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