PCB Trace Width & Current Calculator
Use this free online PCB Trace Width Calculator to determine the required trace width for your target current. Instantly calculate trace resistance, voltage drop, and power dissipation based on IPC-2221 formulas — for both internal and external copper layers.
When designing a PCB, choosing the correct trace width is critical for power delivery reliability. A trace that is too narrow will overheat under load, cause voltage drop, or fail entirely. This free calculator uses the IPC-2221 formula to instantly compute the minimum trace width needed for your target current, based on copper thickness and allowed temperature rise. Results include required width (mil/mm), trace resistance, voltage drop, and power dissipation — for both external and internal copper layers.
Input Parameters
Strictly follows the IPC-2221 standard.
1 oz/ft² of copper thickness is equivalent to 1.378 mils or 0.035 mm.
PCB Trace Width Quick Reference Table
Common trace width requirements for external (top/bottom) layers at 10°C temperature rise, calculated per IPC-2221. Use these values as a quick starting point; for precise results, use the calculator above.
| Current | 0.5 oz Copper | 1 oz Copper | 2 oz Copper | 3 oz Copper |
|---|---|---|---|---|
| 1 A | 23.7 mil0.60 mm | 11.8 mil0.30 mm | 5.9 mil0.15 mm | 3.9 mil0.10 mm |
| 2 A | 61.5 mil1.56 mm | 30.8 mil0.78 mm | 15.4 mil0.39 mm | 10.3 mil0.26 mm |
| 3 A | 107.6 mil2.73 mm | 53.8 mil1.37 mm | 26.9 mil0.68 mm | 17.9 mil0.46 mm |
| 5 A | 217.8 mil5.53 mm | 108.9 mil2.77 mm | 54.4 mil1.38 mm | 36.3 mil0.92 mm |
| 10 A | 566.5 mil14.39 mm | 283.2 mil7.19 mm | 141.6 mil3.60 mm | 94.4 mil2.40 mm |
| 15 A | 991.0 mil25.17 mm | 495.5 mil12.59 mm | 247.7 mil6.29 mm | 165.2 mil4.20 mm |
| 20 A | 1473.6 mil37.43 mm | 736.8 mil18.71 mm | 368.4 mil9.36 mm | 245.6 mil6.24 mm |
Note: Internal (inner layer) traces require approximately 2× the width of external traces for the same current, due to reduced heat dissipation. For 20°C temperature rise, trace widths can be roughly 30–35% smaller than the values above.
Calculation Formulas (IPC-2221)
First, calculate Area (A)
Then, calculate Width (W)
Where k, b, and c are constants resulting from curve fitting to the IPC-2221 curves.
- k = 0.024
- b = 0.44
- c = 0.725
- k = 0.048
- b = 0.44
- c = 0.725
Frequently Asked Questions (FAQ)
What is a PCB Trace Width Calculator?
A PCB Trace Width Calculator is an essential engineering tool used to determine the minimum required width of a copper trace on a Printed Circuit Board (PCB). It ensures that the trace can safely carry a specific amount of electrical current without overheating, preventing board failure or delamination.
How does the IPC-2221 standard work?
The IPC-2221 is the generic standard for printed board design. This calculator uses the proven IPC-2221 charts and formulas to map the relationship between current carrying capacity, copper cross-sectional area, and the allowed temperature rise. It provides the most reliable baseline for standard rigid PCBs.
Why is there a difference between internal and external traces?
External traces (on the top or bottom layers) are exposed to air, allowing them to dissipate heat through convection much more effectively. Internal traces are embedded within insulating core/prepreg materials (like FR4), which trap heat. Consequently, internal traces require significantly more width (more copper area) to carry the same current at the same temperature rise.
What is "Temperature Rise" (Temp Rise)?
Temperature rise refers to the maximum allowed increase in temperature of the trace above the ambient room temperature while operating. For standard FR4 boards, engineers typically design for a 10°C to 20°C temperature rise to maintain long-term reliability.
Can this tool calculate PCB trace resistance and voltage drop?
Yes. After entering your current, copper thickness, temperature rise, and trace length, the calculator automatically outputs trace resistance (in Ω), voltage drop (in V), and power dissipation (in W) for both external and internal layers. This helps you verify that your power delivery network stays within acceptable loss limits before sending your design to fabrication.
How wide should a PCB trace be for 1 amp?
For a 1 A current on a standard 1 oz copper external layer with a 10°C temperature rise, you need a trace width of approximately 11.8 mil (0.30 mm). If the trace runs on an internal layer, the required width increases to about 30.8 mil (0.78 mm). In practice, designers commonly use a conservative 20 mil (0.5 mm) for 1 A signal or power traces to provide a safety margin.
What trace width do I need for 5V power on 1 oz copper?
Trace width depends on current, not voltage — so the question is really "how many amps does your 5V rail carry?" For a typical 5V / 1A load on 1 oz external copper at 10°C rise, use at least 11.8 mil (0.30 mm). For 5V / 3A, widen the trace to 53.8 mil (1.37 mm). Always design for the maximum expected current, including inrush and transient spikes, not the steady-state average.
Is IPC-2221 still the current standard for PCB trace width?
Yes, IPC-2221B (released in 2012) remains the most widely referenced standard for PCB trace width and current capacity calculations in 2026. It applies to rigid, flex, and rigid-flex boards. For high-current or high-density designs, many engineers cross-check IPC-2221 results against IPC-2152 (a more refined 2009 standard based on modern thermal modeling), which often allows narrower traces for the same current due to more accurate heat-dissipation assumptions.