Countersink Depth Calculator
Calculate how deep to drill a countersink so a screw head sits flush, based on head diameter and countersink angle.
About the Countersink Depth Calculator
A countersink is a cone-shaped recess drilled so a flat- or oval-head screw sits flush with (or just below) the surface. This calculator finds how deep to drill that cone based on the screw head's diameter and the included angle of the countersink bit.
Formula: Countersink Depth = Head Diameter ÷ (2 × tan(Countersink Angle ÷ 2)) — derived from the geometry of a cone, where the diameter at any depth equals twice that depth times the tangent of the half-angle.
82° is the standard angle for U.S. wood screws, while 90° is common for metric and machine screws; self-tapping sheet metal screws sometimes use 100° or 120° bits. Always match your calculated depth to your actual bit's marked angle, and sneak up on the final depth on a scrap piece first — drilling slightly shallow and test-fitting avoids an oversized countersink that lets the screw head sink below flush.