This Javascript web calculator calculates the trace width for printed circuit board conductors for a given current using formulas from IPC-2221 (formerly IPC-D-275).

Inputs:
 Current Amps Thickness oz/ft^2 mil mm um

Optional Inputs:
 Temperature Rise Deg C F Ambient Temperature Deg C F Trace Length inch feet mil mm um cm m

Results for Internal Layers:
 Required Trace Width mil mm um Resistance Ohms Voltage Drop Volts Power Loss Watts

Results for External Layers in Air:
 Required Trace Width mil mm um 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