# Sizing Through-hole Vias for Power Traces

I am trying to understand what size vias I should use for my 5V power traces. The trace typical runs at 0.5-3 amps and is 2mm and about 150mm in length. The width is huge, but I do have the extra space and I'd like to have as little resistance as possible since I am using a battery. The power traces only navigate the external layer of the PCB, no inner layers with poor heat transfer used.

But my design software's default via is 0.8 diameter and 0.4 via drill. Should I expect a voltage drop across the via. How will the resistance of this size via compare to my trace's resistance?

Edit: this is a 4 layer PCB, with 1 oz copper weight. Here is a link to my PCB board manufacture's capabilities: capabilities

• There is a via resistance calculator available which may give a direction. Note the answers to this question where you can find some measured values for the resistance of vias. Theory and practice show the same direction but also vary by some amount. If you have room for it, estimate the number of vias and add a few more to gain some margin - plating thickness in vias has some variation over batches ;-) Jan 2 at 19:35

Given the via is a cylinder, the width of a via can essentially be considered as the circumference of the drill diameter, so: $$\\pi\times d\$$.