Calculate the required depth for a screw to sit flush or sub-flush with the material surface.
Fastener Geometry
Required Countersink Depth
Check your diameters (Head must be larger than Hole)
About this calculator
Overview
A countersink is a conical hole enlarged at the surface to allow the head of a flat-head bolt, screw, or rivet to sit flush or below the surface. Precision is key to ensuring the fastener holds correctly without sticking out or being buried too deep.
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Pro Tips
Always drill your pilot hole (clearance hole) before countersinking to ensure the tool stays centered.
If the screw head varies slightly in size, err on the side of a slightly deeper hole.
In soft woods, you can sometimes skip the countersink as the screw will pull itself flush, but this risks splitting the wood.
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Fun Facts
"82° is the standard countersink angle for most flat-head wood and machine screws in the United States."
"Metric countersinks typically use a 90° angle, which is also popular for woodworking internationally."
"Aerospace applications often use 100° to provide more bearing surface on thin materials."
