Circle field notes

Measure twice. Understand why.

Worked geometry guides for people who need a result they can check: clear formulas, complete examples, practical mistakes, and a direct path to the matching calculator.

Latest guides

Useful before it is searchable.

Follow via RSS →

Technical bolt-circle diagram with eight evenly spaced holes, X and Y axes, and a highlighted radius

Workshop geometryJuly 31, 20269 min read

How to Calculate Bolt Circle (PCD) Hole Coordinates: Formula, Example, and Common Mistakes

Calculate evenly spaced bolt-hole X/Y coordinates from PCD, hole count, start angle, direction, and center offset—with a worked 120 mm example.

Read the guide →