Calculate PCB Trace Width by Current

A free browser-based PCB trace width calculator using the IPC-2221 standard. Enter current, copper weight, and allowable temperature rise to get the minimum trace width for internal and external layers. Includes resistance, voltage drop, power loss, and a copper weight comparison table.

How to Calculate PCB Trace Width

Enter current and temperature rise

Set the maximum current the trace must carry and the allowable temperature rise above ambient (typically 10°C for standard designs, 20-30°C for power traces).

Select copper weight and layer

Choose the copper thickness (1oz is most common) and whether the trace is on an external or internal layer.

Read the result

See the minimum trace width in mm and mil, plus resistance and voltage drop if you entered a trace length.

Size your PCB traces correctly with the IPC-2221 standard formulas

Current (A)

Max Temperature Rise (°C)

Copper Weight

Layer Type

Trace Length (mm)

Ambient Temperature (°C)

Result

Width (mm)

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Width (mil)

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Trace Resistance

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Voltage Drop

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Power Loss

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Max Temperature

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Copper Weight Comparison

Features

IPC-2221 compliant calculation for internal and external PCB layers 4 copper weight presets (0.5oz to 3oz) with automatic thickness conversion Trace resistance, voltage drop, and power loss for given trace length Side-by-side comparison table showing trace width for different copper weights

FAQ

What is the IPC-2221 standard?

IPC-2221 is an industry standard for PCB design that provides formulas to calculate the minimum trace width for a given current, based on copper cross-section and allowable temperature rise.

What is copper weight (oz)?

1 oz copper means 1 ounce of copper per square foot, which equals 35 µm (1.4 mil) thickness. Common values: 0.5oz (17.5µm), 1oz (35µm), 2oz (70µm), 3oz (105µm).

Why do internal traces need to be wider?

Internal traces are sandwiched between layers and cannot dissipate heat as well as external traces. The IPC-2221 formula uses a smaller coefficient (k=0.024 vs k=0.048) for internal layers.

What temperature rise should I use?

For standard signal traces: 10°C. For moderate power: 20°C. For high-power traces: 30-40°C. Never exceed the PCB material rating (typically 130°C for FR4).

How accurate is this calculator?

The IPC-2221 formulas are conservative estimates. Real-world performance depends on via placement, adjacent traces, airflow, and solder mask. Always add a safety margin (10-20%) to the calculated width.

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Who is this tool for?

🔌 Electronics Enthusiasts

Published 06 Apr 2026 Updated 21 May 2026