Addendum Dedendum Calculator

Inputs

Known pitch

Pitch value (m)

Number of teeth (z)

Addendum coefficient (cₐ)

Dedendum coefficient (c_b)

Default result

Addendum (a)

2 mm

Pass

Standard full-depth addendum a = m.

Radial height above the pitch circle.

Also computed

Dedendum (b) 2.5 mm

Standard full-depth dedendum b = 1.25m.

Radial depth below the pitch circle.

Whole depth (h_t) 4.5 mm

a + b.

Working depth (h_w) 4 mm

2a for matching standard addenda.

Root clearance (c) 0.5 mm

Dedendum leaves root clearance for a standard mating addendum.

b - a for a mating standard addendum.

Pitch diameter (d) 40 mm

Outside diameter (d_a) 44 mm

Method notes 4 notes

Standard full-depth external spur gears commonly use addendum a = m, dedendum b = 1.25m, whole depth h_t = 2.25m and clearance c = 0.25m.
Diametral pitch converts through m = 25.4/DP. Circular pitch converts through m = p/pi.
Outside diameter d_a = d + 2a and root diameter d_f = d - 2b, where d = m*z.
This is a tooth-proportion screen. Profile shift, internal gears, stub teeth, cutter protuberance, backlash, root fillets and strength rating are separate checks.