Construction

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Countersink Depth Calculator.

Calculate countersink depth from diameters and included angle.

On-device calculationNo signup

Set your values

Results update as you type.

02 / ANSWER

Head diameter

Hole diameter

Included angle

Depth

0.000

includedAngleDegrees

0.000

radialDifference

0.000

Use Cases

Machining and Fabrication

Determine the depth needed to countersink a hole for a flat-head screw or rivet to sit flush with the surface.

Example: For a head diameter of 10 mm, hole diameter of 5 mm, and 90° angle, depth is 2.5 mm.

Quality Control and Inspection

Verify that machined countersinks meet specifications by calculating the expected depth from measured diameters and angle.

Example: Check if a countersink depth of 3 mm matches the required dimensions.

Frequently Asked Questions

How do I calculate countersink depth?: Enter the head diameter, hole diameter, and included angle. The calculator uses the formula: depth = (head diameter - hole diameter) / (2 * tan(included angle / 2)).
What is the included angle in a countersink?: The included angle is the total angle at the tip of the countersink tool, typically 82°, 90°, or 100°. It is the angle between the two opposite sides of the conical cut.
Can I use this calculator for any material?: Yes, the calculation is geometric and independent of material. However, actual machining may require adjustments for material hardness or tool wear.

Tips & Common Mistakes

Tips

Ensure all measurements are in millimeters and the angle in degrees for accurate results.
Use the actual measured head diameter of the fastener, not the nominal size, for precision.
For standard countersinks, common included angles are 82°, 90°, and 100°; verify the correct one.
Double-check your input values, as small errors in diameter or angle can significantly affect depth.

Common Mistakes to Avoid

Using the screw head diameter instead of the countersink head diameter (the larger top diameter).
Entering the angle in radians instead of degrees, leading to incorrect depth.
Forgetting to divide the difference in diameters by 2, which doubles the calculated depth.

Last updated: August 13, 2026

Use Cases

Machining and Fabrication

Determine the depth needed to countersink a hole for a flat-head screw or rivet to sit flush with the surface.

Example: For a head diameter of 10 mm, hole diameter of 5 mm, and 90° angle, depth is 2.5 mm.

Quality Control and Inspection

Verify that machined countersinks meet specifications by calculating the expected depth from measured diameters and angle.

Example: Check if a countersink depth of 3 mm matches the required dimensions.

Frequently Asked Questions

How do I calculate countersink depth?

Enter the head diameter, hole diameter, and included angle. The calculator uses the formula: depth = (head diameter - hole diameter) / (2 * tan(included angle / 2)).

What is the included angle in a countersink?

The included angle is the total angle at the tip of the countersink tool, typically 82°, 90°, or 100°. It is the angle between the two opposite sides of the conical cut.

Can I use this calculator for any material?

Yes, the calculation is geometric and independent of material. However, actual machining may require adjustments for material hardness or tool wear.

Tips & Common Mistakes

Tips

Ensure all measurements are in millimeters and the angle in degrees for accurate results.
Use the actual measured head diameter of the fastener, not the nominal size, for precision.
For standard countersinks, common included angles are 82°, 90°, and 100°; verify the correct one.
Double-check your input values, as small errors in diameter or angle can significantly affect depth.

Common Mistakes to Avoid

Using the screw head diameter instead of the countersink head diameter (the larger top diameter).
Entering the angle in radians instead of degrees, leading to incorrect depth.
Forgetting to divide the difference in diameters by 2, which doubles the calculated depth.

Use Cases

Machining and Fabrication

Determine the depth needed to countersink a hole for a flat-head screw or rivet to sit flush with the surface.

Example: For a head diameter of 10 mm, hole diameter of 5 mm, and 90° angle, depth is 2.5 mm.

Quality Control and Inspection

Verify that machined countersinks meet specifications by calculating the expected depth from measured diameters and angle.

Example: Check if a countersink depth of 3 mm matches the required dimensions.

Frequently Asked Questions

How do I calculate countersink depth?

Enter the head diameter, hole diameter, and included angle. The calculator uses the formula: depth = (head diameter - hole diameter) / (2 * tan(included angle / 2)).

What is the included angle in a countersink?

The included angle is the total angle at the tip of the countersink tool, typically 82°, 90°, or 100°. It is the angle between the two opposite sides of the conical cut.

Can I use this calculator for any material?

Yes, the calculation is geometric and independent of material. However, actual machining may require adjustments for material hardness or tool wear.

Tips & Common Mistakes

Tips

Ensure all measurements are in millimeters and the angle in degrees for accurate results.
Use the actual measured head diameter of the fastener, not the nominal size, for precision.
For standard countersinks, common included angles are 82°, 90°, and 100°; verify the correct one.
Double-check your input values, as small errors in diameter or angle can significantly affect depth.

Common Mistakes to Avoid

Using the screw head diameter instead of the countersink head diameter (the larger top diameter).
Entering the angle in radians instead of degrees, leading to incorrect depth.
Forgetting to divide the difference in diameters by 2, which doubles the calculated depth.