PCB Trace Width Calculator
Calculate the required trace width for a PCB based on current, trace thickness, and allowable temperature rise. Ensure traces are wide enough to handle required current.
1 oz = 0.035mm, 2 oz = 0.07mm
Typical: 10-20°C
How to Use This Calculator
- Enter the current the trace must carry in amperes.
- 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 required trace width in millimeters and mils.
- Use this to design power traces that can safely handle your current requirements.
Trace Width Formula
Required trace width is calculated from current, thickness, and temperature rise using IPC-2221:
Solving for A: A = (I / (k × (ΔT)^b))^(1/c)
Width = A / Thickness
Where k = 0.048, b = 0.44, c = 0.725
Example: 2A current, 0.035mm thickness, 10°C rise: Area ≈ 0.07 mm², Width ≈ 2.0mm. For 5A: Width ≈ 5.0mm.
Full Description
Determining the correct trace width is essential for PCB design, especially for power traces that carry significant current. Traces that are too narrow will overheat, potentially causing failures, delamination, or fire hazards. The IPC-2221 standard provides formulas for calculating required trace width based on current, copper thickness, and allowable temperature rise.
Required trace width increases with current and decreases with copper thickness. For example, a 5A trace requires much wider traces than a 1A trace. Using thicker copper (2 oz instead of 1 oz) allows narrower traces for the same current, but costs more. Temperature rise is also a factor—allowing higher temperature rise (20°C vs 10°C) permits narrower traces but may affect reliability.
This calculator helps you determine required trace width. Enter current, thickness, and temperature rise, and it calculates the minimum trace width needed. Use it when designing power traces, planning PCB layouts, ensuring trace safety, or understanding how current requirements affect trace dimensions. Always add safety margins and consider factors like trace length, ambient temperature, and nearby heat sources.
Frequently Asked Questions
How do I calculate required trace width?
Use the IPC-2221 formula: Width = Area / Thickness, where Area is calculated from current and temperature rise. The formula is: I = k × (ΔT)^b × A^c, solved for A, then Width = A / T.
What trace width do I need for common currents?
Rough estimates for 1 oz copper (0.035mm), 10°C rise: 1A ≈ 0.3mm, 2A ≈ 0.6mm, 5A ≈ 1.5mm, 10A ≈ 3mm. These are approximate—use calculators for accurate values. Higher currents require wider traces or thicker copper.
Can I use multiple parallel traces?
Yes! Multiple parallel traces share current. For example, two 0.5mm traces can carry roughly twice the current of one 0.5mm trace. However, account for current sharing and ensure traces are well-connected at both ends.
How does copper weight affect trace width?
Thicker copper (2 oz, 3 oz) can carry more current for the same width, or the same current with narrower width. 2 oz copper (0.07mm) can carry roughly 2x the current of 1 oz (0.035mm) for the same width. However, thicker copper costs more.