Current capacity, resistance and parasitic inductance of a plated through-hole via.

The barrel is a thin copper tube

A plated through-hole carries current in the copper plated onto the drilled wall. Its cross-sectional area is the annulus between the finished hole and the outside of the plating:

A = π t (D + t)

with drill diameter $D$ and plating thickness $t$ (typically 20–25 µm, ≈ 1 mil). The DC resistance follows from that area and the via length:

R = \frac{ρ L}{A}, ρ_{Cu} = 1.724 \times 1 0^{- 8} Ω \cdot m

How much current can it take?

Treat the barrel like a trace and apply IPC-2221 with the external-conductor constant — a via is exposed to air on the inside and conducts heat into the planes:

I = k Δ T^{0.44} A^{0.725}, k = 0.048 (A in mils^{2})

One via rarely carries much; for power, stitch several in parallel — current and thermal capacity scale with the count. And every via is a small series inductance, which matters for high-speed return paths and decoupling:

L_{via} \approx 0.2 h [ln (\frac{4 h}{d}) + 1] nH (h, d in mm)

That's why a decoupling capacitor's via pair can dominate its effective inductance, and why high-speed signal vias want a nearby ground via for the return current.

PCB Via Calculator

The barrel is a thin copper tube

How much current can it take?

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