PCB Track Width Calculator

Advanced PCB Track Width Tool

Calculation mode

Load current, A

Allowed temperature rise, °C

Ambient temperature, °C

Track location

Copper weight, oz/ft²

Track length, mm

Safety factor

Known track width, mm

Used when capacity mode is selected.

Target maximum voltage drop, V

Track Width Graph

The chart compares estimated required width for external and internal tracks using the selected copper weight and temperature rise.

Formula Used

IPC style current equation:

I = k × ΔT^0.44 × A^0.725

Required copper area:

A = (I ÷ (k × ΔT^0.44))^(1 ÷ 0.725)

Track width:

Width = Area ÷ Copper thickness

Resistance:

R = ρ × Length ÷ Cross-sectional area

Voltage drop and loss:

Vdrop = I × R and Power = I² × R

External tracks use k = 0.048. Internal tracks use k = 0.024. Copper thickness is estimated from copper weight.

How to Use This Calculator

Select whether you want a required width or a capacity check.
Enter the expected current in amperes.
Choose the allowed temperature rise for the copper track.
Select external or internal routing.
Enter copper weight, track length, and safety factor.
Add a known width when checking current capacity.
Press the calculate button.
Review width, resistance, voltage drop, power loss, and warnings.
Download the result as CSV or PDF for records.

Example Data Table

Use Case	Current	Copper	Layer	Temp Rise	Typical Design Note
Sensor supply	0.25 A	1 oz	External	10 °C	Usually narrow, but voltage drop still matters.
Logic rail	1 A	1 oz	External	10 °C	Keep short and check return path.
LED strip feed	3 A	2 oz	External	20 °C	Use wide copper pours when possible.
Motor driver	8 A	2 oz	External	30 °C	Review peak current and connector rating.
Inner power path	4 A	1 oz	Internal	20 °C	Internal copper needs more width for heat.

Why PCB Track Width Matters

A printed circuit board track is more than a copper line. It is a current path. Its width, copper thickness, and route length control heat, voltage loss, and reliability. A narrow track can run hot. A long track can waste power. A heavy load can reduce usable voltage at the device. Good sizing helps the board work under normal load, startup load, and field variation.

Thermal Design Basics

This calculator uses the classic IPC style current equation. It relates current to copper area and allowed temperature rise. External tracks cool better than internal tracks, so they use a higher constant. Copper weight changes thickness. Higher copper weight gives more area for the same visible width. The safety factor increases the design current before sizing. This gives extra margin for tolerance, aging, and enclosure heat.

Electrical Loss Checks

Track width is not only a heating problem. Every copper path has resistance. Resistance creates voltage drop and power loss. The tool estimates resistance from copper resistivity, length, width, thickness, and conductor temperature. It then reports voltage drop, watts lost, current density, and loss per inch. These values help you decide if the track is thermally safe and electrically acceptable.

Practical Layout Advice

Use wider tracks for motors, heaters, battery paths, converters, and connector feeds. Keep high current paths short. Avoid sharp neck downs. Use planes or pours when current is large. Add vias in parallel when current moves between layers. Check connector ratings, fuse ratings, solder mask limits, and manufacturing limits. A calculator gives a strong first estimate. Final boards should still be reviewed with your fabrication rules, enclosure airflow, copper balance, and real temperature tests.

When to Add More Margin

Add margin when the board sits in a sealed box, near hot parts, or inside a vehicle. Add margin for pulsed loads with high average heating. Add margin when copper thickness is uncertain. Also consider inrush current, fault current, and regulatory spacing. A cooler track usually lasts longer and keeps nearby components more stable.

Record your assumptions for each design. Future debugging becomes easier when current, rise, length, and copper weight are saved with exported results.

FAQs

1. What is PCB track width?

PCB track width is the visible width of a copper conductor on a board. It affects current capacity, heat rise, resistance, voltage drop, and manufacturability.

2. Why do internal tracks need more width?

Internal tracks are surrounded by board material. They lose heat less easily than outside copper, so the same current usually needs a wider internal path.

3. What does copper weight mean?

Copper weight describes copper thickness. One ounce copper is about 35 micrometers thick. Higher copper weight increases area and current capacity.

4. Should I use a safety factor?

Yes. A safety factor helps cover tolerance, heat buildup, fabrication variation, aging, and unexpected current. Larger values give wider, cooler tracks.

5. Does this replace thermal testing?

No. It gives a practical estimate. Final products should be checked against fabrication rules, enclosure conditions, airflow, load cycles, and real measurements.

6. Why is voltage drop important?

Voltage drop reduces the voltage available at the load. It can cause weak motors, dim LEDs, unstable regulators, or unreliable logic behavior.

7. Can I use copper pours instead?

Yes. Copper pours are useful for high current paths. They reduce resistance, spread heat, and often improve current return paths.

8. What if my board shop has minimum widths?

Always follow the board shop rules. If the calculated width is below their minimum, use their minimum or a wider track for better margin.