How this calculator works
A uniform rectangular conductor has resistance proportional to length and resistivity and inversely proportional to width times thickness. Correct the reference resistivity with a linear temperature coefficient. Enter the actual trace temperature, including any self-heating; this page does not solve the heat flow. The rectangular model neglects etched sidewall taper, vias and AC skin effects.
Formula
R = rho20[1 + alpha(T - 293.15 K)]L/(width x thickness); voltage drop = IR; dissipation = I²R.
Worked example
A 100 mm long, 1 mm wide, 0.035 mm thick copper trace at 20 Celsius has about 0.0492571 ohms resistance. At 2 A, it drops about 0.0985143 V and dissipates 0.197029 W.
Advertisement
Frequently asked questions
Why does copper resistance rise with temperature?
Electron scattering increases as the metal warms. The coefficient approximates this change near the reference temperature.
Does this include return-path resistance?
No. Calculate each conductor separately and add their resistances for a loop.
Can I use a different conductor?
Yes. Enter its resistivity at 20 Celsius and its temperature coefficient, within the validity of a linear model.