Spur Gear and Pinion Calculations

Diametral Pitch

Key:
D_o = Outside Diameter.
a = Centre distance.
P = Diametral pitch.
N = Number of teeth.
N₁ = Number of teeth gear 1.
N₂ = Number of teeth gear 2.

Outside diameter

D_o = (N + 2) / P

Centre distance

a = (N1 + N2) / (2 * P)

Module

Key:
D_o = Outside Diameter.
a = Centre distance.
m = Module.
z = Number of teeth.
z₁ = Number of teeth gear 1.
z₂ = Number of teeth gear 2.

Outside diameter

D_o = m * (z + 2)

Centre distance

a = m * (z₁ + z₂) / 2