## PCB Trace Width Calculator
*January 31, 2006*

This Javascript web calculator calculates the trace width for printed circuit boards based on a curve fit to IPC-2221 (formerly IPC-D-275). Also see the via calculator.

**New features:**

- Results update as you type
- Several choices of units
- Units and other settings are saved between sessions
- Blog format allows user comments

**Inputs:
**

Current | Amps | |

Thickness |

**Optional Inputs:
**

Temperature Rise | Deg | |

Ambient Temperature | Deg | |

Trace Length |

**Results for Internal Layers:
**

Required Trace Width | ||

Resistance | Ohms | |

Voltage Drop | Volts | |

Power Loss | Watts |

**Results for **External Layers in Air:

Required Trace Width | ||

Resistance | Ohms | |

Voltage Drop | Volts | |

Power Loss | Watts |

**Notes:**

The trace width is calculated as follows:

First, the Area is calculated:

Area[mils^2] = (Current[Amps]/(k*(Temp_Rise[deg. C])^b))^(1/c)

Then, the Width is calculated:

Width[mils] = Area[mils^2]/(Thickness[oz]*1.378[mils/oz])

For IPC-2221 internal layers: k = 0.024, b = 0.44, c = 0.725

For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725

where k, b, and c are constants resulting from curve fitting to the IPC-2221 curves

**For geometry diagrams, click on the pictures below.**

**For frequently asked questions, see the comments.**