PCB Via Current Calculator
Enter your via drill size, copper plating thickness, and how much the board is allowed to heat up. Get the maximum safe current, via resistance, voltage drop, and how many vias to use in parallel. Runs entirely in your browser - nothing uploaded.
Max current - single via (IPC-2221)
1 via = - A
Via resistance ?
milliohms
Voltage drop ?
millivolts at max current
Power dissipated ?
milliwatts at max current
Copper cross-section ?
mil² and mm²
Learn more: how much current a PCB via can carry
A via is a hollow copper tube
A trace's cross-section is its width times its thickness. A via's is a thin ring of plated copper lining the drilled hole. The tool takes the drill diameter, adds the plating on both sides to get the outer diameter, and finds the ring area as pi/4 x (outer squared - drill squared).
For a 0.3 mm drill with 25 micrometers of plating the outer diameter is 0.35 mm, since 25 um on each side adds 0.05 mm in total. The ring is 0.0255 mm2, or 39.6 mil2. The IPC-2221 equation then gives about 1.90 A for a 10 C rise.
Plating thickness changes the answer a good deal. JLCPCB's plating thickness guide lists about 20 um average hole-wall copper for IPC-6012 Class 2 and about 25 um for Class 3, and about 35 um for 1 oz outer copper. In the tool, the same 0.3 mm drill gives 1.60 A at 20 um and 2.48 A at 35 um.
Check against published figures
NextPCB's via design guide says a standard 0.3 mm via with 1 oz plating can typically carry about 1.5 A within safe temperature limits, and recommends via arrays for high current. That is lower than the tool's 2.48 A for 35 um plating, so treat the tool's figure as an upper estimate and leave margin.
The parallel-vias option multiplies one via's current by the count, so four vias of 1.90 A give 7.6 A. That assumes the vias share the current evenly and do not heat each other, which is less true when they sit close together.
Plating, drill size and resistance
Because only the shell carries current, thicker plating adds more copper than a slightly bigger drill. Doubling the plating to 50 um on a 0.3 mm drill raises the ring to 0.0550 mm2 and the current to about 3.3 A. Widening the drill to 0.4 mm at 25 um gives 0.0334 mm2 and about 2.3 A.
Via length affects resistance and not the current figure, which depends on area and temperature rise. Through a 1.6 mm board the 0.3 mm via has a resistance of about 1.08 milliohms. At 1.90 A that is a drop of 2.1 mV and 3.9 mW of heat.
FAQ
Why not use one bigger via?
A bigger via only adds a little ring area. One 0.4 mm via at 25 um carries about 2.3 A in the tool, while two 0.3 mm vias carry about 3.8 A. Several small vias also take up less board space.
Does board thickness change the current capacity?
Not in the formula, which uses cross-section area and temperature rise. A thicker board does give a longer via, so more resistance, voltage drop and heat per via.
What temperature rise should I design for?
The tool offers 10, 20 and 30 C. A 10 C rise is the conservative choice. A larger rise allows more current through the same via, and the via runs hotter. Pick the rise your board can tolerate.