Coordinate Geometry Tool
Bolt Circle Coordinate Calculator
Calculate equal-spacing hole coordinates and adjacent chord with an explicit zero axis and clockwise/counter-clockwise angle direction.
Bolt-circle geometry
| Hole | Pattern angle | X (mm) | Y (mm) |
|---|
Equal angular spacing and chord
This is the centre-to-centre chord between adjacent equally spaced holes, not edge clearance or ligament. Hole diameter is not an input.
Cartesian coordinates
Here αaxis=0° for +X or 90° for +Y; q=+1 for CCW or −1 for CW. This page reports Xc=Yc=0. Add the verified machine centre offset separately.
Why the convention is an input
There is no universal statement that bolt-pattern angles increase clockwise. Drawing view, machine coordinates and software conventions differ. The selected zero axis and direction are part of every result and copied output.
EN 1092-1 boundary
EN 1092-1:2018 is current steel-flange context and includes flange types, dimensions, tolerances and bolting. The previous page’s small “PN16” table mixed incorrect PCD/count values and has been removed. This calculator does not select a flange from DN/PN; enter only dimensions taken from the exact licensed standard, supplier drawing or measured part.
Verification: check every point satisfies √(X²+Y²)=D/2, adjacent chord equals D·sin(π/N), and the closing chord from the last point to the first is identical.
Professional engineering instruments and calculators.
