Keep the hole definition explicit
Drilled diameter and finished hole diameter are different dimensions in a plated hole. The appropriate dimension depends on the question being reviewed. This calculator uses whichever hole value you enter; it cannot infer whether that value describes the drill tool, a finished plated hole or another manufacturing definition.
Record that interpretation next to the result. For a production discussion, confirm the hole definition and the fabricator’s aspect-ratio convention rather than presenting a ratio without context.
Calculate the nominal ring
For concentric circles, the nominal annular ring is half the difference between pad diameter and hole diameter. A 0.6 mm pad around a 0.3 mm hole gives (0.6 − 0.3) / 2 = 0.15 mm. The calculator rejects a hole larger than the pad.
The result assumes perfect centering. It does not deduct drill wander, layer registration, etching or dimensional tolerance. A zero or small nominal ring is a geometric result, not evidence of an acceptable manufactured land.
Calculate the aspect ratio
Dividing a 1.6 mm board thickness by a 0.3 mm hole gives approximately 5.33:1. This simple ratio helps describe hole geometry, but it does not establish the plating process or acceptable manufacturing limit.
Blind, buried and laser-drilled structures require their own depth and diameter definitions. Do not substitute total board thickness for the drilled depth of a partial-depth structure. This tool is intentionally limited to the dimensions you provide.
Carry the right questions into review
Review pad size, drill and finished-hole requirements, plating, layer connections and the intended via treatment together. If a via sits in a component land, filling and capping requirements may be critical to assembly. If a hole is mechanical, clarify whether plating is intended.
Send the drill map and fabrication notes with the layout. Ask for a review of registration margin and production requirements rather than treating a positive calculated ring as a completed DFM check.