Convert between oz, µm, mil, and mm for PCB copper weight
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| Weight | oz/ft² | µm | mil | mm |
|---|---|---|---|---|
| 1/4 oz (Ultra-thin) | 0.25 | 8.8 | 0.34 | 0.009 |
| 1/2 oz (Standard signal) | 0.5 | 17.5 | 0.69 | 0.018 |
| 1 oz (Most common) | 1 | 35.0 | 1.37 | 0.035 |
| 2 oz (Power/high current) | 2 | 70.0 | 2.74 | 0.070 |
| 3 oz (Heavy copper) | 3 | 105.0 | 4.11 | 0.105 |
| 4 oz (Heavy copper) | 4 | 140.0 | 5.48 | 0.140 |
| 6 oz (Extreme power) | 6 | 210.0 | 8.22 | 0.210 |
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1 oz copper refers to the weight of copper spread over 1 square foot, which equals 35 µm thickness.
This is the most common copper weight for standard PCBs, suitable for most signal traces and moderate current applications.
Copper thickness directly affects current carrying capacity, heat dissipation, and impedance. Choosing the right copper weight is essential for reliable PCB performance.
Heavier copper requires adjusted design rules for reliable manufacturing:
Copper thickness is a physical measurement of conductor height on a PCB layer. A copper weight callout refers to the equivalent mass of copper distributed over one square foot of area, which is why 1 oz copper is a shorthand rather than a direct dimensional unit.
In fabrication planning, copper thickness is a major input for etch compensation, impedance modeling, and current carrying capacity. It also interacts with minimum trace and spacing capability, especially for heavy copper boards.
1 oz copper refers to the copper mass spread across one square foot of laminate, which corresponds to roughly 35 micrometers of finished copper thickness.
Fabrication drawings, impedance work, and current calculations often require thickness in linear units rather than weight-per-area notation.
No. Heavier copper lowers resistance, but it also changes trace geometry, etching limits, and manufacturability for fine-pitch designs.
Thicker copper increases cross-sectional area, which usually reduces DC resistance and temperature rise for a given current.
Power conversion, motor control, battery management, and thermal spreading applications commonly move above standard 1 oz copper.