PCB Trace Current Calculator
Calculate the maximum current a PCB trace can carry based on trace width, thickness, and allowable temperature rise. Ensure traces can handle required current without overheating.
1 oz = 0.035mm, 2 oz = 0.07mm
Typical: 10-20°C
How to Use This Calculator
- Enter the trace width in millimeters.
- Enter the trace thickness (copper thickness, typically 0.035mm for 1 oz copper).
- Enter the allowable temperature rise in °C (typically 10-20°C).
- The calculator displays the maximum current the trace can safely carry.
- Use this to ensure traces are sized appropriately for your current requirements.
Trace Current Formula
Maximum current is calculated using IPC-2221 formulas based on trace area and temperature rise:
Where I = current (A), k = 0.048, b = 0.44, c = 0.725, ΔT = temperature rise (°C), A = trace cross-sectional area (mm²). Example: 0.5mm width, 0.035mm thickness, 10°C rise: Area = 0.0175 mm², I ≈ 1.5A.
Full Description
Calculating maximum trace current is essential for PCB design to prevent overheating, trace damage, and reliability issues. Traces that carry too much current will heat up, potentially causing failures, delamination, or fire hazards. Understanding current capacity helps you design safe, reliable PCBs.
Current capacity depends on three main factors: trace width (wider traces have more cross-sectional area), trace thickness or copper weight (thicker copper carries more current), and allowable temperature rise (higher temperature rise allows more current but may affect reliability). The IPC-2221 standard provides formulas and tables for calculating current capacity based on these factors.
This calculator helps you determine maximum trace current. Enter trace width, thickness, and temperature rise, and it calculates the maximum safe current. Use it when designing power traces, planning PCB layouts, ensuring trace safety, or understanding how trace dimensions affect current capacity. Always add safety margins and consider factors like trace length, ambient temperature, and nearby heat sources.
Frequently Asked Questions
How do I calculate maximum trace current?
Maximum current depends on trace width, thickness (copper weight), and allowable temperature rise. Wider and thicker traces can carry more current. The IPC-2221 standard provides formulas based on trace cross-sectional area and temperature rise.
What is copper weight (oz)?
Copper weight (1 oz, 2 oz, etc.) refers to the thickness of copper on the PCB. 1 oz = 0.035mm (1.4 mils), 2 oz = 0.07mm (2.8 mils). Heavier copper (2 oz, 3 oz) can carry more current but costs more. Most PCBs use 1 oz copper.
What temperature rise should I use?
Typical: 10-20°C for most applications. Higher temperature rise allows more current but may cause reliability issues. For high-reliability applications, use 10°C. For less critical applications, 20°C is acceptable. Always consider ambient temperature.
How does trace width affect current capacity?
Current capacity is approximately proportional to trace width. Doubling the width roughly doubles current capacity. However, the relationship isn't perfectly linear due to thermal effects. Use calculators or IPC-2221 tables for accurate values.