What is a PCB antipad?

An antipad is the ring of removed copper on a power/ground plane around a via, so the via passes through the plane without shorting to it. Not the same as via ampacity but related to via placement.

How wide should PCB traces be for high current?

See the trace width calculator. Rule of thumb: 1 A on 1 oz external copper needs ~0.3 mm at 10 °C rise. Vias have separate limits and often bottleneck first.

How many vias for a power rail?

Compute your total current draw, then look up single-via capacity for your fab's standard barrel + plating. Divide with a 20–30% safety margin.

Via Current Capacity Calculator (IPC-2152)

Max current for a plated-through-hole via, by barrel diameter, plating thickness, and allowed temperature rise.

BARREL DIA

PLATING

µm

TEMP RISE

°C

PARALLEL VIAS

Result

2.21 A per via · 2.21 A total

0.4 mm × 25 µm plating · 1 via in parallel

Single-via capacity: 2.211 A
Total (parallel): 2.211 A
Barrel cross-section: 48.69 mil²

Tip: add parallel vias to increase capacity roughly linearly.

Design a board with correctly-sized vias →

Method & assumptions

Effective conductor: a plated-through-hole via is a thin-walled cylinder. Cross-section ≈ π · d_barrel · t_plating.

Combined with the IPC-2221 thermal formula (external constant k=0.048), this gives max current for a given temperature rise. Multiple parallel vias scale current capacity roughly linearly. Typical fab plating: 20–35 µm (0.8–1.4 mil).

How to calculate current-carrying capacity in a PCB via

Treat the via barrel as a thin-walled cylinder with cross-section π·d·t (d = barrel diameter, t = plating thickness). Feed this cross-section into the IPC-2221 external-layer formula for the desired temperature rise. Result is the single-via ampacity; parallel vias multiply capacity linearly.

Why via ampacity matters

A trace can carry 3 A comfortably, but if it necks down to a single 0.3 mm via to reach the other layer, that via might only carry 1.5 A safely. Undersized vias on power rails are one of the most common causes of thermal failure on otherwise correctly-designed boards.

Rules of thumb

For a standard 0.4 mm barrel with 25 µm plating and 10 °C rise, expect roughly 1.5 A per via. Double the vias to double the current. Power vias on high-current rails should always be verified against this number, not left as router defaults.

Frequently asked

How to calculate current-carrying capacity in a PCB via?: Compute the barrel cross-section (π × diameter × plating thickness), then apply the IPC-2221 formula for external layers. Multiple parallel vias scale capacity linearly.
What is a PCB antipad?: An antipad is the ring of removed copper on a power/ground plane around a via, so the via passes through the plane without shorting to it. Not the same as via ampacity but related to via placement.
How wide should PCB traces be for high current?: See the trace width calculator. Rule of thumb: 1 A on 1 oz external copper needs ~0.3 mm at 10 °C rise. Vias have separate limits and often bottleneck first.
How many vias for a power rail?: Compute your total current draw, then look up single-via capacity for your fab's standard barrel + plating. Divide with a 20–30% safety margin.

Next step

In PCBEditor, via sizes come from the board's via classes, and the design-rule check flags any via that breaks your fab's drill or ring limits.