Measurement convention: zero degrees is at 12 o'clock and positive angles move clockwise. Coordinates are measured from the bolt-circle center, with positive X right and positive Y up.
Bolt-circle inputs
Center-to-center distance between adjacent holes--
| Hole | Angle | X | Y |
|---|
What the calculator does
The bolt-circle diameter, also called pitch-circle diameter or PCD, passes through every hole center. Adjacent-hole spacing is the straight-line center distance between neighboring holes. If a hole diameter is supplied, the calculator also shows the outside edge diameter of the hole pattern.
Measure before using the result
Check more than one pair of holes when working from a used gasket. Elongated holes, torn edges, camera perspective, and an off-center ruler can create misleading measurements. If the count is even, measuring between opposite hole centers is usually a stronger PCD check than measuring adjacent holes and calculating backward.
Need a complete tracing?
The printable kit includes rulers, diameter references, and space to record the machine and component.