# PCB Via Estimator

> Estimate plated via resistance and power loss Estimate a plated copper via barrel’s resistance, voltage drop, and power loss at 20 °C.

Part of usefulweb.app (https://usefulweb.app/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://ohmforgepcbviaestimator.usefulweb.app/ (interactive tool at https://ohmforgepcbviaestimator.usefulweb.app/tool)
- JSON API: POST https://ohmforgepcbviaestimator.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://ohmforgepcbviaestimator.usefulweb.app/api/v1/tool)
- OpenAPI: https://ohmforgepcbviaestimator.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://ohmforgepcbviaestimator.usefulweb.app/mcp - tool `ohmforge_pcb_via_estimator`

## Inputs
- finishedHoleMm (number): Finished hole diameter - Diameter of the empty hole after plating, not the drill diameter.
- platingMm (number): Finished copper plating thickness - Copper thickness in the barrel; 0.025 mm = 25 µm.
- lengthMm (number): Conducting via length - Length of the plated barrel carrying the current.
- currentA (number): Current

## Method
- For finished hole diameter D and plating thickness t, the cylindrical barrel cross-section is the exact annulus A = π(D + t)t.
- Converts millimeters to meters and estimates R = ρL/A with nominal copper resistivity 1.72 × 10⁻⁸ Ω·m at 20 °C. Computes DC voltage drop I × R and loss I² × R.

## Limits
- Ideal DC copper barrel at 20 °C. This is not a current-capacity, thermal, signal-integrity or fabrication check. It excludes pads, traces, contact resistance, plating variation and heating. Numerical bounds are safeguards, not manufacturing limits; confirm the finished plating and design with your fabricator.