PCB Trace Width Calculator

Calculate the minimum trace width for your PCB design using IPC-2152 and IPC-2221 standards. Fast, accurate, and free to use.

PCB trace width refers to the measurement of the thin copper strips on a circuit board that connect components and carry electrical current. This fundamental parameter determines how much current a trace can safely handle without overheating or causing circuit failure. The trace width directly impacts current capacity, thermal management, signal integrity, and overall circuit performance.

When designing printed circuit boards, adequate trace width is essential to ensure the desired amount of current can be transported without overheating and damaging your board. Inadequate trace sizing can result in thermal overload, voltage drop, signal degradation, and unnecessary design complexity. For most manufacturers, the minimum trace width should be 6mil or 0.152mm, though designers commonly use 10-12 mil or 0.254-0.3 mm traces for tolerance.

Key Points :

What is a Trace Width Calculator, and Why Should You Care?

Think of the copper traces on your circuit board as tiny highways for electricity. The trace width calculator tells you how wide to make those highways to prevent traffic jams.

The Simple Analogy: A Water Pipe for Electrons
Imagine trying to push a river’s worth of water through a garden hose. It’s not going to work. The pressure would be immense, and the hose would likely burst. Electricity flowing through a copper trace works in a similar way.

What Happens if Your Trace is Too Thin?
This is the dangerous part. Pushing too much current (amps) through a trace that’s too narrow generates a lot of heat due to resistance. This can cause the trace to literally burn up, destroying your board, damaging expensive components, and even creating a fire hazard.

What Happens if Your Trace is Too Wide?
This isn’t dangerous, but it’s inefficient. Overly wide traces waste valuable board space, making it much harder to route other signals, especially on a compact design. The goal is to find the “Goldilocks” width: just right for the current it needs to carry.

Let’s Calculate a Trace Width Together: A Real-World Example

Theory is great, but let’s walk through a real-world scenario you’ll definitely encounter: designing a power input for a USB-C powered device.

The Scenario: A 5V, 2A USB-C Power Input
We’re building a project that will be powered by a standard USB-C adapter. The USB spec says we need to handle up to 5 Volts at 2 Amps. We need to figure out how wide the main power trace from the USB-C connector to the rest of the circuit needs to be.

Let’s fire up the PCB Trace Width Calculator.

Step 1: Entering the Current
This is the most critical input. We know our device requires a maximum of 2 Amps. I’ll enter 2 into the “Current” field.

Step 2: Choosing Your Copper Thickness
Most prototype and hobbyist-grade PCBs use a copper thickness of 1 oz/ft². This is the standard, default option at virtually all board houses like JLCPCB or PCBWay. If you don’t know, it’s almost certainly 1 oz.

I’ll leave the “Thickness” dropdown set to the default of 1 oz/ft².

Step 3: Deciding on a “Safe” Temperature Rise
This number is how much hotter you are willing to let the trace get above the air temperature around it.

• 10°C: A very conservative and safe choice. I use this for sensitive designs or anything I want to be extra reliable.
• 20°C: A more standard and perfectly acceptable choice for most non-critical applications.

For this example, I’ll choose a safe 10 °C rise. This keeps things cool and builds in a nice safety margin.

Step 4: Setting the Ambient Temperature
This is the one people get wrong all the time. This is NOT the temperature of your room. It’s the expected air temperature inside your project’s enclosure when it’s running. Electronics generate heat, so it’s always warmer inside the box.

A safe bet for a closed plastic case is around 40°C. I’ll enter 40 °C.

Step 5: Is Your Trace Internal or External?
The calculator needs to know if the trace is on an outer layer (top or bottom) or buried on an inner layer.

• External traces can dissipate heat into the air more easily.
• Internal traces are trapped, so they need to be wider for the same current.

Our power trace will be on the top layer, so I’ll select External Layer.

The Results Are In: Here’s What It All Means

After plugging in our numbers, we get our answer.

Reading the Output
The calculator tells us we need a Required Trace Width of about 0.72 mm, or 28.4 mil. I’ll round that up to a clean 30 mil.

But What About Resistance and Voltage Drop?
The tool also gives you some other useful data. It shows a tiny resistance and a voltage drop of only 11.8 mV (millivolts). This is excellent—it means we won’t lose a significant amount of our 5V supply just getting it across the board.

Common Mistakes and Pro-Tips (Learned the Hard Way)

• Forgetting That Ambient + Rise = Total Temp: In our example, 40°C Ambient + 10°C Rise = 50°C final trace temperature. Standard FR-4 PCB material is typically rated to at least 105°C, so we are well within a safe margin. You must keep this total in mind.
• The Difference Between IPC-2221 and IPC-2152: This calculator uses the older IPC-2221 standard. There’s a newer, more complex standard called IPC-2152. Honestly? For 95% of projects, IPC-2221 is perfectly fine and often more conservative (safer). It’s the industry workhorse for a reason.
• Don’t Forget About Vias!: If your high-current trace needs to switch from one layer to another, it has to go through a “via” (a plated hole). Vias also have current limits! For 2A, a single standard-sized via is not enough. You’d need to use multiple vias (a technique called “via stitching”) to handle the current safely.

Okay, I Have the Number. Now What?

So, the calculator told us to use a 30 mil trace. You need to tell your PCB design software (like KiCad, Altium, or Eagle) to use that width.

The best way to do this is by setting up “Net Classes” or “Design Rules.” You can create a rule called something like “Power_HighCurrent” and assign it a width of 30 mil. Then, you just assign your 5V power net to that class.

This way, your software automatically uses the correct width every time you route that power trace, ensuring your design matches your calculation.

So, what’s the bottom line?

Designing a PCB can feel complex, but tools like the tracewidthcalculator.com make critical safety decisions incredibly simple. It’s not about being an electrical engineer with decades of experience; it’s about being a diligent designer who checks their work.

Bookmark this tool. The next time you route a power line, take the 30 seconds to plug in the numbers. It’s the cheapest and fastest insurance you can get for your project’s success.

What’s the trickiest power design you’ve had to work on? Share your experience in the comments below