PCB Via Current Capacity Calculator (IPC-2221)
Estimate how much current a plated through-hole via array can carry, plus the rough DC drop and thermal load. Good for first-pass sizing and fabrication discussions, not final sign-off on a critical power path.
Quick start examples
Drill size and plating thickness dominate barrel copper area. Pad diameter mainly affects annular ring and fabrication margin.
Inputs
Geometry and thermal target for the array.
Values also auto-update as you edit them.
Capacity check
Maximum current capacity
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Run the calculation to see whether the array has comfortable margin, is near limit, or needs more vias.
Recommendation
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The tool targets about 20 percent margin when it suggests a larger array.
Current per via
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Safety margin
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Barrel area
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Finished hole
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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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Array view
Quick visual split of current across the array.
Fabrication checks
Annular ring
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Max plating before closure
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Warnings
No warnings.
Model notes
IPC-2221 is useful for quick sizing, but not a substitute for fab guarantees or final verification.
- Use guaranteed minimum plating if current margin is tight.
- Include copper planes and thermal spreading in final judgment.
Save the calculation for review
Useful when you want to drop the result into notes, chat, or KiCad rules.
Formula notes
IPC-2221 via estimate
This tool uses the IPC-2221 style relation between allowed temperature rise and plated barrel cross-section.
Why drill size dominates
The copper that carries current is the plated cylinder on the hole wall, so the simplified barrel area follows approximately pi x drill x plating.
Practical rule: if the current path matters, ask the board house for guaranteed minimum plating and finished hole, then check that worst-case geometry instead of nominal targets.
Frequently asked questions
How many vias do I need for a power transition?
Start with the required current, then keep a practical positive margin. Many designs still round up for symmetry and fabrication tolerance.
Why does pad diameter barely change the current result?
The plated barrel carries the current, so drill circumference and plating thickness dominate the simplified cross-section. Pad diameter mainly affects annular ring robustness.
Is this enough for final sign-off?
No. Use it as a first-pass estimate, then combine it with fabrication data, copper spreading, ambient conditions, and where needed more detailed analysis.