PCB calculators / Layout & fabrication
Free tool · PreBuild Engineering
PCB via current and resistance calculator
Find out how many vias your power path needs, and how much heat one via can move.
Inputs
mm
µm
mm
°C
A
Result
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Why it matters
A single small via often carries less current than the trace feeding it, and a via array is the cheapest way to move heat from an exposed pad into inner planes.
Formula
Barrel area A = π/4 × ((d + 2t)² − d²)
I = 0.048 · ΔT^0.44 · A^0.725 [A in mil²]
R = ρ · L / A, θ = L / (k_Cu · A), k_Cu = 385 W/m·K
Design tips
- Thermal vias under an exposed pad work in parallel: θ total ≈ θ per via ÷ number of vias.
- Tented or plugged vias under pads avoid solder wicking during reflow.
Results are engineering estimates from standard formulas and published approximations. Always confirm against component datasheets, your fabricator's capabilities and, for critical designs, simulation or measurement.