PCB via current calculator

The barrel is treated as a copper annulus of cross section pi times drill times plating, and that section is run through the IPC-2221 trace curve for an outer layer at your allowed temperature rise. Resistance uses annealed copper over the board thickness, corrected for temperature. This is geometry math, not a rating: filled or tented vias, microvias, thermal spokes, and shared copper all change the real answer, and no standard publishes a via current limit. De-rate generously for anything that has to survive.