Bolt circle / anchor layout

What this calculator does

Enter how many anchor bolts sit on a circle, the bolt-circle diameter and the angle of the first bolt; the page lists the X-Y coordinate of every bolt from the circle's center, the angle between bolts, and the chord — the straight tape distance between adjacent bolts that the field crew actually lays out.

Worked example

8 bolts on a 24" bolt circle, first bolt at 0°: bolts every 45°; bolt 1 at (12.000, 0.000), bolt 2 at (8.485, 8.485), bolt 3 at (0.000, 12.000). Chord between adjacent bolts = 24 × sin(22.5°) = 9.184".

Common questions

Where is the origin?

The center of the bolt circle, X to the right, Y up. Rotate the whole pattern by changing the start angle; 0° puts the first bolt on the +X axis.

Does it check bolt spacing or edge distance?

No. It is a layout aid: coordinates and chords. Minimum spacing and edge distance come from the anchor design and the base plate — check them separately.

Why give the chord as well as the coordinates?

A template maker and a field crew set bolts with a tape between bolts, not from an origin. The chord is the number they need; the coordinates are for the drawing.