The tool calculates the resistance of a copper PCB trace (also called or track) based on formulas and graphs contained in a standards document [1], given the trace length, width, thickness, and ambient temperature. The same calculation can be applied to busbars. Trace resistance calculation is important because it allows an assessment of how much power the trace itself can dissipate.

Resistance calculation

The internal/external wiring resistance of the PCB is calculated according to the following formula：

Here: R is the trace resistance [Ω] ρ is the resistivity parameter, which for copper is 1.7E-6 [Ω · cm] L is the trace length [cm] T is the trace thickness [cm] W is the trace width [cm] α is the resistivity temperature coefficient, which for copper is 3.9E-3 [1/°C] T_TEMP is the trace temperature [°C]

Example 1

Enter L = 5 inches W = 4 mil T = 3 oz/ft ² T _AMB = 38 °C

Output R = 0.213 Ω

Example 2

Enter L = 10.5 inches W = 4.6 mil T = 5.8 oz/ft ² T _AMB = 37.5 °C

Output R = 0.200 Ω

IPC-2221A “General Standards for Printed Board Design”