🔌 PCB Trace Width Calculator (IPC-2221)
Calculate minimum copper trace width for your PCB design
Live PCB Trace Visualizer
Calculations based on IPC-2221 generic standard. For high-frequency or high-reliability designs, consult IPC-2152 and your PCB manufacturer's capabilities.
Understanding PCB Trace Width Calculations
Designing a Printed Circuit Board (PCB) requires careful calculation of trace widths to prevent overheating and potential board failure. If a trace is too thin for the current it carries, it will act like a fuse and burn out. Our free PCB Trace Width Calculator uses the industry-standard IPC-2221 formula to help engineers, students, and hobbyists determine the minimum safe copper width for their designs.
Step-by-Step Instructions
- Current (Amps): Enter the maximum continuous current the trace will carry. Use the slider to see the effect in real-time.
- Temperature Rise (°C): How much hotter than ambient temperature the trace is allowed to get. 10°C is a standard conservative value; 20°C is common for power electronics.
- Copper Weight: Select the thickness of the copper foil. 1 oz/ft² (35 µm) is the industry standard for most PCBs.
- Layer Type: External layers dissipate heat better into the air, allowing for slightly thinner traces compared to internal layers.
- Check the Visualizer: Watch the copper trace on the green PCB grow thicker as you increase the current or lower the temperature rise limit.
Understanding Your Results
- Min. Trace Width: The absolute minimum width required to carry your current without exceeding your temperature limit. Always add a safety margin (e.g., +20%) in your actual CAD design.
- Cross Section: The area of the copper in square mils. This is the core value calculated by the IPC-2221 formula before dividing by thickness.
- Resistance: The electrical resistance per inch of the trace. Useful for calculating voltage drop in long power traces.
- Current Density: The amount of current per square millimeter. High current density can lead to electromigration over time.
Frequently Asked Questions
IPC-2221 is the generic standard on printed board design. It provides the empirical formulas used to calculate trace width based on current, copper thickness, and allowable temperature rise. Note: For very high currents, the newer IPC-2152 standard is recommended, but IPC-2221 remains the industry workhorse for general design.
A mil is a unit of length equal to one-thousandth of an inch (0.001 inch or 0.0254 mm). PCB manufacturing and copper weights (like 1 oz) are traditionally measured in mils and ounces per square foot.
External traces are exposed to air, which acts as a coolant (convection). Internal traces are sandwiched between FR4 fiberglass layers, which are thermal insulators. Therefore, internal traces need more copper cross-section to dissipate the same amount of heat.
While wider traces have lower resistance, using excessively wide traces for signal lines can cause impedance mismatches, increase parasitic capacitance, and waste valuable board space. Only use calculated widths for power and ground nets.