PCB Copper Weight: 0.5oz vs 1oz vs 2oz

Choosing the right copper weight for your PCB is one of those decisions that seems simple until you realize how much it affects everything else—trace width, current capacity, cost, manufacturability, and even impedance. Whether you're designing a low-power IoT sensor or a beefy motor controller, understanding the trade-offs between 0.5oz, 1oz, and 2oz copper is essential.

This guide compares calculated electrical estimates and fabrication trade-offs. The numerical model and its limits are stated below.

Calculation Basis and Sources

Electrical tables use the site's calculateTraceWidth model: I = k × ΔT^0.44 × A^0.725, with A in mil², k = 0.048 externally and 0.024 internally, and 1oz = 1.37 mil. R = ρL/A with ρ = 1.724 × 10⁻⁸ Ω·m at 20°C and a 0.393%/°C increase; trace resistance uses T = 20°C + ΔT. Values are rounded estimates, not test results.

This is the calculator's IPC-2221-style approximation, not an IPC-2152 thermal simulation. The public IPC-2152 contents identify separate treatment of copper weight, board material, environment, and copper planes. Verify the finished design under its actual thermal conditions.

What Is Copper Weight (And Why oz/ft²)?

Copper weight is measured in ounces per square foot (oz/ft²)—a unit that confuses newcomers because it describes weight rather than thickness. The logic is simple: take 1 square foot of copper, weigh it, and that's your copper weight.

The table uses the calculator convention of 1.37 mil per oz, with metric values rounded for display. Nominal foil labels such as 35 μm are approximate; specify finished copper thickness and tolerance with the fabricator.

Current Capacity: The Main Event

The biggest reason to choose heavier copper is current capacity. Thicker copper has a larger cross-sectional area, which means more room for electrons to flow and better heat dissipation.

Notice the pattern? Doubling the copper weight halves the required trace width in this model. For high-current applications, the difference between 0.5oz and 2oz copper can mean the difference between a feasible design and an impossible routing nightmare.

Use our Trace Width Calculator to estimate widths for your current, temperature rise, and copper weight combination.

0.5oz Copper: The Lightweight Champion

1oz Copper: The Industry Standard

1oz copper is a common option, but the fabrication drawing must specify the finished copper thickness. Verify the offered stackup rather than relying on an unspecified default.

2oz Copper: The Power Handler

2oz copper can reduce the width needed for a given current or improve heat spreading. Whether it is needed depends on available width, cooling, and voltage-drop limits.

Complete Side-by-Side Comparison

Qualitative comparison only: resistance assumes equal width, length, and temperature. Fabrication, RF, and thermal suitability depend on the complete stackup.

Resistance and Voltage Drop: The Hidden Cost

Copper weight directly affects resistance, which determines voltage drop along your traces. This matters a lot for power delivery, especially in low-voltage systems.

External layer, 10°C rise above 20°C, 10 inches = 254 mm. Widths below are rounded; resistance and losses use the unrounded calculated cross-section.

Notice something interesting? When you size traces properly for the same current and temperature rise, the voltage drop is similar regardless of copper weight. The advantage of heavier copper is that you can achieve this with narrower traces, saving board space.

At fixed width and length, heavier copper lowers resistance. The following table solves the same external-layer power law for temperature rise at 5A, then uses that rise to adjust resistance. It is an estimate, not a measured temperature:

Manufacturing Considerations

Etching Limitations

Thicker copper requires longer etching time, which causes more undercutting. This is why a fabricator may require larger minimum trace and space with heavier copper:

Minimum trace/space is a fabrication-process capability, not a fixed property of oz/ft². Obtain the fabricator's rules for the selected finished copper, layer, and etching process.

Plating and Hole Quality

Finished trace copper and via barrel plating are separate fabrication specifications. Do not infer barrel thickness from a 2oz foil label; confirm minimum plating with the fabricator. See the Via Sizing Guide for details.

Cost Impact

The cost increase for heavier copper varies by fab house and quantity:

Request quotes for the same stackup, finish, tolerances, and quantity. No universal percentage premium follows from copper weight alone.

Impedance and Signal Integrity

Copper weight affects trace impedance because it changes the geometry. Thicker copper means a different height-to-width ratio, which changes characteristic impedance.

A 50Ω width requires dielectric permittivity, dielectric height, finished copper thickness, solder mask, and a specified impedance model. Copper weight alone is insufficient; confirm the geometry with the fabricator rather than using an unqualified width table.

For controlled impedance designs, always specify your copper weight when requesting stackup calculations from your fab house. Use our Impedance Calculator to see how copper thickness affects your trace geometry.

Using Mixed Copper Weights

Modern PCB manufacturing allows different copper weights on different layers. This is common in power electronics where you might want:

• 2oz copper on outer layers for power traces and heat dissipation
• 1oz copper on inner signal layers for routing density
• 0.5oz copper on high-speed layers for controlled impedance

Application Selection Guide

Rule of thumb, not from a standard: these are illustrative starting points, not current ratings or application requirements. Size each actual trace and verify thermal conditions.

Quick Decision Guide

These screening questions are rules of thumb, not limits from a standard.

Common Mistakes to Avoid

For more PCB design pitfalls, read our guide on 10 Common PCB Trace Width Mistakes.

Conclusion

Choosing the right copper weight is about matching your design requirements to material capabilities. 1oz copper remains the sweet spot for most applications—it's the default for good reason. Go lighter (0.5oz) when you need fine features or controlled impedance. Go heavier (2oz+) when you need to move serious current or dissipate heat.

The key is to calculate your actual requirements using tools like our Trace Width Calculator and let the numbers guide your decision. Don't over-specify copper weight "just in case"—it adds cost and reduces routing flexibility.