PCB Trace Current Calculator

Calculate the maximum current capacity for PCB traces based on width, thickness, and temperature specifications.

Calculate Your PCB Trace Current Calculator

Trace Width

Copper Weight

Temperature Rise (°C)

Trace Location

External Layer

Internal Layer

Understanding PCB Trace Current Capacity

The current-carrying capacity of PCB traces is a critical factor in circuit board design. When electrical current flows through a trace, it generates heat due to the trace's resistance. If the current exceeds the trace's capacity, excessive heating can damage the PCB by causing delamination, warping, or even burning.

Factors Affecting Current Capacity

Trace Width

The width of a trace directly affects its current-carrying capacity. Wider traces have lower resistance and better heat dissipation, allowing them to handle more current. As a rule of thumb, doubling the width doesn't quite double the current capacity due to thermal factors.

Copper Thickness (Weight)

PCB copper thickness is typically specified in ounces per square foot (oz/ft²), where 1 oz/ft² equals approximately 35 μm (1.4 mils) thickness. Thicker copper can carry more current due to increased cross-sectional area and improved heat dissipation.

Temperature Rise

The allowable temperature rise above ambient is a design constraint that affects current capacity. Higher allowable temperature rises permit more current, but excessive temperatures can damage the PCB material and nearby components. Most designs target 10-20°C rise for reliability.

Trace Location

Traces on external layers can dissipate heat more effectively than internal traces, which are surrounded by PCB material. Internal traces typically have about 30% less current capacity than external traces of the same dimensions.

The IPC-2152 Standard

The industry standard for PCB current capacity calculations is IPC-2152, "Standard for Determining Current-carrying Capacity in Printed Board Design." This standard replaced the older IPC-2221 and provides more accurate charts and formulas based on extensive thermal testing of various trace configurations.

The IPC-2152 calculations account for:

Trace width and thickness
Allowable temperature rise
Trace location (internal vs. external)
Trace length
Board thermal properties

Design Guidelines

Apply Safety Margin: Design traces to handle at least 20% more current than expected maximum loads to account for variations in temperature, manufacturing, and operating conditions.
Consider Power Planes: For high-current paths (above 5A), consider using power planes or copper pours instead of traces.
Mind Vias: When changing layers, use multiple vias in parallel for high-current paths, as vias have significantly less current capacity than traces.
Thermal Relief: Use appropriate thermal relief connections when connecting traces to large copper areas to prevent soldering difficulties.

Approximate Current Capacity

For quick reference (assuming 10°C rise and 1oz copper on external layer):

Trace Width	Approximate Current
10 mil	1.0 A
20 mil	1.6 A
50 mil	2.9 A
100 mil	4.5 A
200 mil	7.1 A

Remember that these are approximations, and actual values may vary based on specific board construction, ambient conditions, and trace length. For critical applications, always refer to the full IPC-2152 standard or use specialized PCB design tools.

Related Calculators

PCB Trace Width Calculator

Calculate optimal PCB trace width based on current requirements and temperature rise.

PCB Trace Resistance Calculator

Calculate electrical resistance of PCB traces based on dimensions and material properties.

Battery Capacity Calculator

Calculate battery capacity in mAh or Wh based on current and discharge time.

PCB Impedance Calculator

Calculate the characteristic impedance of PCB traces based on dimensions, materials, and layout.

Frequently Asked Questions

The current-carrying capacity of a PCB trace depends on several factors including the trace width, thickness (copper weight), temperature rise allowance, ambient temperature, and whether the trace is internal or external. For example, a 10-mil wide, 1 oz copper trace on an external layer can typically handle around 0.5-1A with a 10°C temperature rise. The IPC-2152 standard provides comprehensive charts and guidelines for determining appropriate current limits.

Current capacity increases with trace width, but not linearly. Doubling the width doesn't double the current capacity due to thermal dissipation factors. The relationship follows approximately a power function where current capacity increases proportionally to width raised to a power between 0.5-0.7, depending on other conditions like trace thickness and allowed temperature rise.

Copper thickness has a significant impact on current capacity. Heavier copper (like 2 oz or 3 oz compared to standard 1 oz) provides more cross-sectional area for current flow and better heat dissipation. Doubling the copper thickness from 1 oz to 2 oz increases current capacity by approximately 50-60%, not 100%, due to thermal factors.

Most PCB designs target temperature rises between 10°C and 30°C above ambient. Critical applications typically use lower temperature rises (10°C) for safety and reliability, while less critical applications might allow up to 30°C rise. Higher temperature rises can accelerate aging of the PCB material, cause delamination, and affect nearby components, so they should be carefully considered.

Yes, internal traces have significantly lower current capacity than external traces of the same dimensions. This is because internal traces are surrounded by PCB material, which insulates them and prevents efficient heat dissipation. As a rule of thumb, an internal trace might have only 50-70% of the current capacity of an identical external trace due to these thermal constraints.

Vias have significantly less current-carrying capacity than traces due to their smaller cross-sectional area. A standard via might handle only 1-2A, regardless of how wide the connecting traces are. For high-current paths, designers often use multiple vias in parallel, larger via sizes, or filled/plated vias. A good rule of thumb is that each standard via can handle approximately 0.5A per 10 mil of diameter.

Share This Calculator

Found this calculator helpful? Share it with your friends and colleagues!