PCB Via Current Capacity Calculator (IPC-2221)
Calculate via current capacity and thermal properties using IPC-2221 standard. Determine how many vias you need for your power traces.
⚙️ Parameters
Expected current through vias
Via pad outer diameter
Hole diameter before plating
Copper plating on barrel wall
Typical: 5-10°C for normal operation
Vias in parallel (array/stitching)
PCB thickness (standard: 1.6mm)
📊 Results
Maximum Current Capacity
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Safety Margin
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Resistance
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Voltage Drop
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Power Dissipation
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Thermal Resistance
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📐 Visual Reference
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Export results for use in KiCad or documentation
Theory & Formulas
IPC-2221 Via Formula
Vias carry current through the plated copper barrel. The IPC-2221 standard uses a modified formula for via current capacity:
I = Current per via in Amperes
0.093 = Via-specific constant (differs from traces)
ΔT = Temperature rise above ambient in °C
A = Plated barrel cross-sectional area in square mils
Barrel Area Calculation
The plated barrel area is calculated from the via geometry:
Average Diameter = (Via Diameter + Drill Diameter) / 2
Circumference = π × Average Diameter
Barrel Area = Circumference × Plating Thickness
Standard plating: 25µm (1 mil). Heavy plating (35-50µm) increases current capacity.
Via Arrays
Multiple vias in parallel increase current capacity:
Total Current = Current per Via × Number of Vias
Total Resistance = Resistance per Via / Number of Vias
💡 Design Tip: Always use multiple vias for power connections. A via array distributes current and improves thermal performance. Aim for 20% safety margin minimum.
Frequently Asked Questions
How many vias do I need for my power trace?
Enter your current requirement and via dimensions, then check the "Safety Margin" result. If it's negative or below 20%, the calculator will recommend the number of vias needed. General rule: at least 2-4 vias for power connections, more for high current (>2A).
What's standard via plating thickness?
Standard is 25µm (1 mil). Most PCB manufacturers guarantee at least 18µm minimum. For high-current applications, specify 35µm or 50µm heavy copper. Check with your manufacturer for capabilities.
Should vias be in a line or grid pattern?
Grid pattern is better for high current as it distributes heat more evenly. For via stitching (thermal or ground), grid is preferred. For connecting traces, linear arrays along the trace path work well.
Can I use smaller vias to save space?
Smaller vias carry less current per via, so you'll need more vias in parallel. Standard 0.6mm/0.3mm vias are a good balance. Microvias (0.2-0.3mm) need more aggressive arrays. Always verify with this calculator.