Enter a hole diameter and included angle, then specify either chamfer width or depth. The calculator derives the other dimension and the countersink OD. Includes a live SVG cross-section diagram.
Last updated April 2026
The most common countersink angle is 82 degrees (included) for flat head screws per ANSI standards. Aerospace fasteners typically use 100 degrees per NAS and MS specs. European DIN fasteners use 90 degrees. Always match the countersink angle to the fastener head angle for proper flush seating and full bearing contact.
Chamfer depth equals the chamfer width multiplied by the tangent of half the included angle. For a 45-degree chamfer (90-degree included), depth equals width since tan(45) is 1.0. For other angles, use depth = width x tan(angle/2). This relationship also determines the countersink OD when applied to a hole edge.