# PCB Trace Width Calculator

Created by Álvaro Díez
Reviewed by Dominik Czernia, PhD and Jack Bowater
Based on research by
Standard IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Boards The Institute for Interconnecting and Packaging Electronic Circuits (March 2004)
Last updated: Sep 28, 2022

When creating a PCB (Printed Circuit Board), it is essential to know how wide should the PCB traces be for your application, and that's why we built the PCB trace width calculator.

In this calculator, we will show you how to calculate the trace width of a PCB for both internal and external traces. We will also tell you by how much you can expect the temperature of your PCB trace to rise by, as well as the resistance and maximum current that the trace can stand.

## PCB traces - a brief overview

Almost all electronic equipment nowadays uses a PCB, or Printed Circuit Board. They are reasonably cheap to produce and use, and significantly reduce the clutter in and space of your project/device.

The traces in a PCB (metal channels that act as "cables") vary in their location (external or internal) and properties. Since the traces are generally made of copper, which is relatively expensive, it is important to know how wide your PCB traces should be before designing them. You can do this easily with our PCB trace width calculator.

## How wide should PCB traces be?

Your PCB trace width is determined by the requirements of your project. If you are after pure performance, you should make them as wide as possible, as this reduces resistance and heat buildup.

In the real world, both space and materials have a cost, so the answer to the question How wide should PCB traces be? is always given as the narrowest possible value for your application.

The ideal PCB trace width for your situation depends on the location of the trace (inside or over the substrate), as well as any temperature and current limitations you have put on your application. Let's see how to calculate the trace width on a PCB!

## How to calculate the width of a PCB trace?

When it comes to the equations, you simply need to use the following:

$W = \frac{A}{1.378t}$

where

• $W$ is the PCB trace width, in thousands of an inch (mil);
• $A$ is the cross section area, in mils2; and
• $t$ is the trace thickness, in oz/ft2.

To obtain $A$, we can use:

$A = {\bigg(\frac{I}{kT_{\text{rise}}^b}\bigg)}^{\frac{1}{c}}$

where

• $I$ is the maximum current through the PCB trace;
• $T_{\text{rise}}$ is the maximum temperature rise of the PCB trace (in °C over ambient temperature); and
• $b = 0.44$, and $c = 0.725$ are fixed parameters.

The value of $k$ depends on the location of the trace; for internal traces $k = 0.024$, and for external PCB traces $k = 0.048$.

You can calculate the resistance, $R$, of the trace using:

$R = \frac{\rho L}{A'} (1 + \alpha(T_{\text{temp}} - 25\degree\text{C})$

where

• $L$ is the length of the trace, in cm;
• $A'$ is the cross section area, in cm2;
• $\rho = 1.7 \times 10^{-6} \ \Omega \ \text{cm}$ is the resistivity of copper;
• $\alpha = 3.9 \times 10^{-3} \ \degree \text{C}^{-1}$ is the resistivity temperature coefficient for copper; and
• $T_{\text{temp}}$ is the temperature of the PCB trace.

Doing all this by hand can be confusing, which is why we created the PCB trace width calculator.

## How to use the PCB trace width calculator?

Using the PCB trace width calculator is rather simple; all you have to do is follow these steps:

1. Select the location of the PCB trace (internal/external).
2. Input the trace thickness, maximum current, and maximum temperature rise.
3. Obtain your results (PCB trace width and cross-section area).
4. Do you want more? Use Advanced mode to reveal some extra options.
5. Fill in the length of the trace and ambient temperature.
6. Enjoy your extra outputs, like the resistance, temperature, voltage drop, and power dissipation of the trace.

Isn't it easy? Now that you have all the parameters you could ever hope for, it's time to do the fun part: building!

If you're involved in an electronics project, the PCB trace width isn't the only calculator that will help you. Here is a short list of potentially useful calculators for your endeavors:

All the calculations were performed as described in the standard IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Boards.

Álvaro Díez
The trace is...
internal
Inputs
Max. current
A
Trace thickness (T)
oz/ft²
Max. desired temperature rise
°F
Output
Trace width (W)
mil
Cross section
mil²
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