PCB Trace Width Calculator Formula
Understand the math behind the pcb trace width calculator. Each variable explained with a worked example.
Formulas Used
Trace Width (external)
trace_width_mils = area_mils2 / thickness_milsTrace Width (mm)
trace_width_mm = area_mils2 / thickness_mils * 0.0254Cross-Section Area
cross_section_mils2 = area_mils2Variables
| Variable | Description | Default |
|---|---|---|
current_a | Current(A) | 3 |
temp_rise_c | Allowed Temperature Rise(°C) | 10 |
copper_weight_oz | Copper Weight(oz) | 1 |
thickness_mils | Derived value= copper_weight_oz * 1.378 | calculated |
area_mils2 | Derived value= pow(current_a / (0.048 * pow(temp_rise_c, 0.44)), 1 / 0.725) | calculated |
How It Works
PCB Trace Width (IPC-2221)
Formula
Area = (I / (k x dT^0.44))^(1/0.725)
Width = Area / Thickness
For external layers k = 0.048. Copper thickness at 1 oz = 1.378 mils. This is for external (outer) layers; internal layers need wider traces due to less cooling.
Worked Example
3 A current, 10C rise, 1 oz copper.
current_a = 3temp_rise_c = 10copper_weight_oz = 1
- 01Thickness = 1 x 1.378 = 1.378 mils
- 02Area = (3 / (0.048 x 10^0.44))^(1/0.725) = ~79.6 mils^2
- 03Width = 79.6 / 1.378 = ~57.8 mils = ~1.47 mm
Ready to run the numbers?
Open PCB Trace Width Calculator