PCB Via Current Calculator Formula

Understand the math behind the pcb via current calculator. Each variable explained with a worked example.

Use the PCB Via Current Calculator

Formulas Used

Current Capacity

current_capacity_a = 0.048 * pow(temp_rise_c, 0.44) * pow(cross_section_mils2, 0.725)

Cross-Section

cross_section = cross_section_mils2

Via Resistance

resistance_mohm = 0.67 * via_length_mm / (via_circumference_mils * plating_mils * 0.000645)

Variables

VariableDescriptionDefault
via_diameter_mmVia Outer Diameter(mm)0.6
plating_thickness_umPlating Thickness(µm)25
via_length_mmVia Length (board thickness)(mm)1.6
temp_rise_cAllowed Temperature Rise(°C)10
via_circumference_milsDerived value= pi * via_diameter_mm / 0.0254calculated
plating_milsDerived value= plating_thickness_um / 25.4calculated
cross_section_mils2Derived value= via_circumference_mils * plating_milscalculated

How It Works

PCB Via Current Capacity

Approach

A via is a hollow copper cylinder. Its cross-section is:

A = pi x D x t_plating

Apply the IPC-2221 trace formula to this cross-section to estimate current capacity. For high current, use multiple vias in parallel.

Worked Example

0.6 mm diameter via, 25 um plating, 1.6 mm board, 10C rise.

via_diameter_mm = 0.6plating_thickness_um = 25via_length_mm = 1.6temp_rise_c = 10
  1. 01Circumference = pi x 0.6 / 0.0254 = 74.2 mils
  2. 02Plating = 25 / 25.4 = 0.984 mils
  3. 03Area = 74.2 x 0.984 = 73.0 mils^2
  4. 04Current = 0.048 x 10^0.44 x 73^0.725 = ~2.8 A

Ready to run the numbers?

Open PCB Via Current Calculator