Countersink Depth Calculator
Get the exact countersink depth for flat-head screws. Whether you are working with 82°, 90°, 100°, or 120° heads, this tool ensures a perfect flush fit every time. Includes options for slightly recessed or fully below-surface installation.
Diameter of the screw head (top face)
Diameter of the pilot hole for the screw body
D = (H - P) / (2 x tan(θ/2))
Where:
H = Screw head diameter
P = Pilot hole diameter
θ = Countersink angle
Example (82°):
D = (0.322 - 0.125) / (2 x tan(41°))
D = 0.197 / (2 x 0.8693)
D = 0.113"
D = (0.322 - 0.125) / (2 x tan(41°))
D = 0.197 / 1.7386
D = 0.1133"
Rounded: 7/64" (0.1094")
Head height: ~0.1133"
Set countersink tool to 0.113" depth for flush fit.
What is the standard countersink angle for common screws?
The most common countersink angle is 82 degrees for American standard flat-head screws. Metric screws typically use 90 degrees. Sheet metal screws often use 100 degrees, and some specialized applications use 120 degrees. Always match the countersink angle to the screw head angle for a flush fit.
How do I measure countersink depth correctly?
Countersink depth is measured from the top surface of the material to the deepest point of the tapered hole. For a flush fit, the depth should be exactly the height of the screw head. Use a depth micrometer or a properly set countersink tool with a stop for consistent results.
What happens if my countersink is too deep or too shallow?
If too shallow, the screw head will protrude above the surface, creating a tripping hazard and an unprofessional appearance. If too deep, the screw head sits below the surface, weakening the material and potentially causing cracks. A perfect countersink brings the screw head exactly flush with or slightly below the surface.
Do I need different countersink depths for different materials?
Yes, material properties affect countersink depth. Softer materials like wood can accommodate slightly deeper countersinks. Harder materials like metal require precise depth control to avoid weakening the structure. For brittle materials like ceramic or glass, use shallow countersinks with minimal force.
🔗 Related Calculators
📐 Formula
D = (H - P) / (2 x tan(θ/2))
Where:
H = Screw head diameter
P = Pilot hole diameter
θ = Countersink angle
Example (82°):
D = (0.322 - 0.125) / (2 x tan(41°))
D = 0.197 / (2 x 0.8693)
D = 0.113"
📝 Example Calculation
D = (0.322 - 0.125) / (2 x tan(41°))
D = 0.197 / 1.7386
D = 0.1133"
Rounded: 7/64" (0.1094")
Head height: ~0.1133"
Set countersink tool to 0.113" depth for flush fit.