PCB Via Current Calculator

Accurately determine the current‑carrying capacity of plated through‑hole vias. Based on the industry‑standard IPC‑2221 formula with thermal reference to IPC‑2152. Includes cross‑section visualization, voltage drop, total power dissipation, and parallel via optimization.

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Inner finished diameter after plating (mm)
Cu
Typical: 20–35 µm (1 oz = 35 µm)
?
PCB thickness, affects resistance
Above ambient (typical 10–30°C)
Used for copper resistivity correction
For current sharing / stitching
IPC-2221 coefficient based on layer
? Presets: ? Signal Via (0.2mm) ⚡ Power Via (0.45mm) ? High Current (0.6mm, 2oz) ?️ Microvia (0.15mm) ? Industrial (ΔT=30°C)
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Via Current Capacity: Engineering Deep Dive

This calculator implements the widely used IPC‑2221 empirical formula and references thermal principles from IPC‑2152 for more realistic modelling of vias. A via acts as a vertical conductor; its current rating depends on copper cross‑section, allowable temperature rise, board thermal conductivity, and plating uniformity.

? Core Formula (IPC‑2221):

I = k · ΔT0.44 · A0.725

Where I = current (A), ΔT = temperature rise (°C), A = cross‑sectional area of copper barrel (mil²), k = empirical constant: 0.048 for external layers, 0.024 for internal layers (conservative for vias).

Cross‑sectional area A (mm²) = π × tcu × (Dfin − tcu), with tcu in mm. Convert to mil²: 1 mm² = 1550 mil².

Resistance includes temperature coefficient (α = 0.00393 /°C) based on ambient temperature.

Typical Current Capacities (k=0.048, ΔT=20°C)

  • 0.2 mm via / 20 µm plating → ≈ 1.4 A (area ~18 mil²)
  • 0.3 mm via / 25 µm plating → ≈ 2.4 A (area ~34 mil²)
  • 0.45 mm via / 35 µm plating → ≈ 4.5 A (area ~71 mil²)
  • 0.6 mm via / 50 µm plating → ≈ 7.3 A (area ~134 mil²)

* Values are approximate; use the calculator above for exact numbers based on your inputs.

Professional Design Guidelines

  • Current density: Vias can tolerate higher current densities than traces (often 60‑100 A/mm²). This calculator warns above 70 A/mm², and flags >80 A per via (consider arrays or larger vias).
  • Parallel vias & current sharing: When using multiple vias, current distribution is rarely perfectly uniform due to layout and plating variations. Always add 15‑20% more vias than the theoretical number.
  • Plating thickness: For high‑reliability designs (automotive/aerospace), specify 25 µm minimum even if IPC Class 2 allows 20 µm.
  • Thermal relief: Use solid connections for power vias, but thermal spokes for soldering.

Frequently Asked Questions

Larger diameter increases copper cross‑sectional area, which directly increases current rating. Doubling diameter from 0.2 to 0.4 mm roughly doubles the current capacity (if plating thickness stays constant).

Consumer electronics: 10‑20°C. Industrial/automotive: 30°C with derating. Avoid >40°C to prevent solder joint fatigue.

Yes, it shows total current and total power. However, real‑world current sharing is not perfect – we recommend adding 15% extra vias as a safety margin.

The calculator is based on the IPC‑2221 formula (which remains the industry standard for via current estimation) with thermal insights from IPC‑2152. For exact IPC‑2152 compliance, additional board‑specific factors (copper plane proximity, board thickness corrections) are required. This tool provides a reliable, conservative estimate suitable for most designs.
Engineered for PCB designers. Verified against Saturn PCB Toolkit and IPC‑2221 reference tables.