Chamfer Diameter Calculator (Angle, Depth & Width)

Calculate chamfer diameter or axial depth from base diameter, chamfer size, and included angle for external OD or internal bore chamfers.

What do you want to solve for?

Chamfer location

Internal chamfers open up to a larger diameter; external chamfers step down to a smaller one.

Units

Hole diameter (required)

Chamfer size is given as

On a standard 45° chamfer the width per side and axial depth are equal.

Chamfer width per side (required)

Chamfer / tool included angle

Related Calculators

Chamfer Diameter Formula

The calculator uses two formulas, one for each mode.

Mode 1: Diameter from chamfer size C

D c hamfer = Dₛtart \pm 2 \times C

Mode 2: Axial Z depth from included angle

Z = |D c hamfer - D b ase| / (2 \times tan(θ / 2))

D_start: starting diameter before the chamfer is cut
D_chamfer: diameter measured at the chamfered face
D_base: base diameter of the bore or shaft below the chamfer
C: chamfer size, radial distance per side (the leg length on a 45° chamfer)
θ: included angle of the chamfer or countersink
Z: axial depth the tool travels along the part axis

Use Diameter from C when the print calls out a chamfer like 1.5 × 45° and you need the diameter at the face. Add 2C for an internal chamfer (bore opens up). Subtract 2C for an external chamfer (OD shrinks).

Use Depth from angle when you know the base diameter and the target chamfer diameter and need the Z depth for a CNC program. The included angle covers standard 90° chamfers and countersinks at 60°, 82°, 100°, and 120°, plus any custom angle.

Common Chamfer and Countersink Values

Standard chamfer callouts and the diameter change they produce per side:

Callout	C (radial)	Diameter change (2C)
0.5 × 45°	0.5 mm	1.0 mm
1.0 × 45°	1.0 mm	2.0 mm
1.5 × 45°	1.5 mm	3.0 mm
2.0 × 45°	2.0 mm	4.0 mm
1/32 × 45°	0.03125 in	0.0625 in
1/16 × 45°	0.0625 in	0.125 in

Standard countersink angles and where they are used:

Included angle	Typical use
60°	Lathe centers, deburring
82°	Inch flat head screws (UNC/UNF)
90°	Metric flat head screws, general chamfers
100°	Aerospace flat head fasteners
120°	Sheet metal countersinks, drill point match

Worked Examples

Example 1: External 45° chamfer. A shaft is 25 mm OD with a 1.5 × 45° chamfer. The diameter at the chamfered face is 25 − 2(1.5) = 22 mm. The Z depth equals C, so 1.5 mm.

Example 2: 82° countersink for a #10 flat head screw. The pilot hole is 5.0 mm and the head needs to sit flush at a 9.4 mm face diameter. Depth = (9.4 − 5.0) / (2 × tan(41°)) = 4.4 / 1.738 = 2.53 mm of axial travel.

FAQ

Is C the leg length or the hypotenuse? C is the leg length, measured radially per side. On a 45° chamfer the axial depth equals C. On other angles they differ.

Why does the diameter grow on an internal chamfer? The chamfer cuts material away from the bore wall, so the opening at the face is wider than the base bore. Add 2C instead of subtracting.

Does the calculator account for tool tip radius or dwell? No. It returns the theoretical geometry. Add a small Z offset in your CAM program if your tool has a flat or radius at the point.

Can I use inches and millimeters together? Yes. Each input has its own unit selector. The result is converted to the unit you choose and also shown in mm and inches.