Via Size Calculator
Enter the current, the via drill size, the copper plating thickness, the board thickness and the temperature rise you allow. The calculator gives the current each via carries, how many you need and their resistance.
- Current per via
- Vias needed
- Resistance and drop
Standard plating is about 25 µm (1 mil). Use 20 µm if you are unsure, to be safe.
A via carries current through the thin copper plating on its wall. The copper is a thin tube, so even a fairly large via has little cross-section. A 0.3 mm via with 25 µm plating carries about 2 A for a 10 °C rise, so higher currents need several vias side by side.
Via current chart
25 µm plating, 10 °C rise. Search for a drill.
| Drill (mm) | Current (A) | Vias for 3 A |
|---|---|---|
| 0.2 | 1.46 | 3 |
| 0.25 | 1.69 | 2 |
| 0.3 | 1.9 | 2 |
| 0.4 | 2.31 | 2 |
| 0.5 | 2.69 | 2 |
| 0.6 | 3.06 | 1 |
| 0.8 | 3.74 | 1 |
| 1 | 4.37 | 1 |
IPC-2221 external formula. Results are approximate.
Drill size and current
25 µm plating, 10 °C rise. Slide the drill size.
The section shows the plated barrel through the board, with pads top and bottom.
How to size vias
Barrel copper. Step through it.
Drill and plating
Barrel size.
Thermal vias under hot parts work the same way, but are spaced in a grid to spread heat.
Through, blind or buried
Via types. Compare them.
Top to bottom.
Outer to inner layer.
Inner layers only.
Via-in-pad, filled and capped, lets you place vias under fine-pitch parts.
Before layout
Via checks. Tick each item.
Tick each item as you go.
Ask your board maker for their real plating thickness and minimum drill size.
What you get
Via sizing. Each tile explains one result.
For the current.
Amps.
sq mil.
mΩ each.
Minimum size.
Several smaller vias often carry more current than one big via, because they have more barrel wall in total.
Frequently Asked Questions
No question matches that search.
How much current can a via carry?
About 1 to 2 A for a small via with standard plating, at a 10 °C rise.
How many vias do I need?
Divide your current by the current one via carries, then round up.
Does via size affect current?
Yes. A larger drill gives more copper round the barrel.
What plating thickness is standard?
About 25 µm, or 1 mil, for most fabs.
What standard is used for via current?
IPC-2221, applied to the barrel's copper area.
What is the resistance of a via?
Usually a few milliohms or less.
Should I use one large via or many small ones?
Several smaller vias spread out usually work better and are more reliable.
Enough copper for the current
Work out what one via carries, use enough of them and spread them out. Your power paths stay cool and reliable.
More size calculators
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