PCB Trace Current Calculator

The PCB Trace Current Calculator tells you the maximum current a copper trace on a circuit board can carry before it overheats — a critical check when designing printed circuit boards for any powered device. Enter your trace width, copper thickness, trace location (external or internal layer), maximum temperature rise, and ambient temperature to get the maximum current capacity in amps. Add an optional trace length to also see trace resistance, voltage drop, power dissipation, and maximum operating temperature.

mil

Width of the copper trace

Standard copper thickness options

Internal layers have lower current capacity

°C

Maximum allowed temperature increase above ambient

°C

Operating environment temperature

mm

For resistance and voltage drop calculations

Results

Maximum Current

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Cross-Sectional Area

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Trace Resistance

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Voltage Drop

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Power Dissipation

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Maximum Temperature

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Frequently Asked Questions

What is the difference between internal and external PCB traces?

External traces are on the outer layers of the PCB and have better heat dissipation due to air exposure. Internal traces are buried within the PCB layers and have reduced current capacity because heat dissipation is limited by the surrounding dielectric material.

How does copper thickness affect current carrying capacity?

Thicker copper layers can carry more current because they have a larger cross-sectional area. Standard thicknesses are 0.5, 1, 2, and 3 oz/ft², with 1 oz/ft² being the most common. Each doubling of thickness roughly doubles the current capacity.

What temperature rise should I allow for my PCB traces?

A common design rule is to limit temperature rise to 10°C above ambient for reliable operation. Higher temperature rises (up to 40°C) may be acceptable for non-critical applications, but this reduces component lifespan and reliability.

Is this calculator based on industry standards?

Yes, this calculator uses the IPC-2221 standard formulas for PCB trace current capacity. IPC-2221 is the widely accepted industry standard for printed circuit board design guidelines and current carrying calculations.

Why is trace length important for current calculations?

Trace length affects resistance, voltage drop, and power dissipation but not the maximum current capacity itself. Longer traces have higher resistance, leading to greater voltage drops and power losses at the same current level.

How accurate are these current capacity calculations?

The IPC-2221 formulas provide good estimates for most applications, typically within 10-20% of actual values. Real-world factors like PCB stackup, via thermal effects, and component heat generation can affect actual current capacity.

What happens if I exceed the calculated current limit?

Exceeding the current limit will cause the trace temperature to rise beyond the specified limit, potentially leading to PCB delamination, component damage, solder joint failure, or even trace burnout in extreme cases.

Should I consider voltage drop when designing PCB traces?

Yes, voltage drop becomes important for power delivery traces, especially in low-voltage high-current applications. Even if current capacity is adequate, excessive voltage drop can cause circuit malfunction or reduced performance.