PCB Copper Weight to Thickness — Table & Calculator
Convert copper weight (oz/ft²) to thickness in µm and mil, get sheet resistance, and estimate a trace's DC resistance.
Copper weight reference
Thickness and sheet resistance are computed for pure copper at 20 °C — 1 oz/ft² spreads to 34.8 µm.
| Weight | Thickness (µm) | Thickness (mil) | Sheet resistance (mΩ/□) | Typical use |
|---|---|---|---|---|
| 0.5 oz | 17.4 | 0.69 | 0.991 | Inner layers, fine-pitch HDI |
| 1 oz | 34.8 | 1.37 | 0.495 | The default for outer layers |
| 2 oz | 69.6 | 2.74 | 0.248 | Power sections, motor drivers |
| 3 oz | 104.4 | 4.11 | 0.165 | Heavy current, thick-copper fabs |
| 4 oz | 139.2 | 5.48 | 0.124 | Heavy copper (specialist fabs) |
| 5 oz | 174.0 | 6.85 | 0.099 | Heavy copper (specialist fabs) |
| 6 oz | 208.8 | 8.22 | 0.083 | Heavy copper (specialist fabs) |
What copper weight means
PCB copper is specified by weight: the ounces of copper rolled onto one square foot. One ounce works out to a 34.8 µm (1.38 mil)layer, and everything scales linearly from there.
R = R_sheet × (length ÷ width)
Sheet resistance makes trace resistance easy to reason about: every "square" of trace — any stretch as long as it is wide — has the same resistance regardless of its size. A 1 oz trace 50 squares long is 50 × 0.495 ≈ 25 mΩ.
Related
Size a trace for current with thePCB trace current calculator, check vias with thevia properties calculator, or estimate wire runs with thewire voltage drop calculator.