PCB Via Current Calculator Formula
Understand the math behind the pcb via current calculator. Each variable explained with a worked example.
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_mils2Via Resistance
resistance_mohm = 0.67 * via_length_mm / (via_circumference_mils * plating_mils * 0.000645)Variables
| Variable | Description | Default |
|---|---|---|
via_diameter_mm | Via Outer Diameter(mm) | 0.6 |
plating_thickness_um | Plating Thickness(µm) | 25 |
via_length_mm | Via Length (board thickness)(mm) | 1.6 |
temp_rise_c | Allowed Temperature Rise(°C) | 10 |
via_circumference_mils | Derived value= pi * via_diameter_mm / 0.0254 | calculated |
plating_mils | Derived value= plating_thickness_um / 25.4 | calculated |
cross_section_mils2 | Derived value= via_circumference_mils * plating_mils | calculated |
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.
- 01Circumference = pi x 0.6 / 0.0254 = 74.2 mils
- 02Plating = 25 / 25.4 = 0.984 mils
- 03Area = 74.2 x 0.984 = 73.0 mils^2
- 04Current = 0.048 x 10^0.44 x 73^0.725 = ~2.8 A
Frequently Asked Questions
How many vias for high current?
Divide required current by per-via capacity and add margin. 10 A typically needs 4-5 standard vias.
Does via fill help?
Copper-filled vias have much higher current capacity and lower thermal resistance than hollow plated vias.
What about thermal vias?
Thermal vias transfer heat between layers to heat sinks. Use many small vias in a grid pattern under thermal pads.
Ready to run the numbers?
Open PCB Via Current Calculator