pcb width trace calculator

PCB Trace Width Calculator (IPC-2221)

Estimate the required copper trace width for current carrying capacity and temperature rise.

Current (A)

Allowed Temperature Rise (°C)

Copper Weight (oz/ft²)

Layer Type

Trace Length (cm, optional)

Length is used for estimated resistance and voltage drop calculations.

Why trace width matters in PCB design

Trace width is one of the most important electrical and thermal decisions on a printed circuit board. If a trace is too narrow, it can overheat, increase voltage drop, reduce efficiency, and in extreme cases fail. If it is too wide, you may waste board area, increase routing congestion, and make layout more difficult.

A practical PCB trace current calculator helps you quickly choose a starting width based on current, copper thickness, and acceptable temperature rise. This page focuses on the common IPC-2221 approach, which many designers use for first-pass sizing.

How this PCB trace width calculator works

The calculator uses the IPC-2221 empirical equation:

I = k × (ΔT^0.44) × (A^0.725)

Where:

I = current in amps
ΔT = allowable temperature rise in °C
A = conductor cross-sectional area in mil²
k = 0.048 for external layers, 0.024 for internal layers

After solving for area, width is calculated from:

Width (mil) = Area (mil²) / Copper thickness (mil)

Copper thickness is estimated from copper weight using approximately 1 oz ≈ 1.378 mil ≈ 35 µm.

Inputs explained

1) Current (A)

Enter the steady-state current your trace must carry. For pulsed loads, you can still use this tool as a baseline, then validate with thermal simulation or measurement.

2) Allowed temperature rise

This is how much hotter the trace is allowed to run above ambient. Lower rise means a wider trace. Typical conservative values are 10°C to 20°C for many mixed-signal and power boards.

3) Copper weight

Common values are 1 oz and 2 oz copper. Thicker copper reduces required width for the same current.

4) Internal vs external layers

External layers cool better due to airflow and radiation, so they can usually carry more current for a given width than internal layers. That is why the calculator uses different constants.

Practical design tips

Add margin: After calculation, increase width by 20-50% when space allows.
Check fabrication limits: Very narrow traces may violate your PCB manufacturer rules.
Mind connectors and vias: A wide trace feeding a small via can still bottleneck current.
Reduce voltage drop: Long power traces may need extra width even if thermal rise is acceptable.
Use copper pours: Planes and pours can significantly improve thermal and current performance.

Example workflow

Suppose you need to route 3 A on a 1 oz external layer and want 10°C rise. Enter the values, calculate, and then round up to a practical design rule (for example, from 48 mil to 60 mil). If the route is long, review estimated voltage drop and consider even wider copper.

Limits and engineering judgment

No online PCB track width calculator replaces full thermal analysis in high-power designs. Results can vary due to board stackup, adjacent copper, airflow, duty cycle, ambient temperature, and manufacturing tolerance. Use this as a strong starting point, then validate with prototypes and measurements.