| Symbol | Description | Units | . . . . | Symbol | Description | Units |
| a | Addendum | mm | . . . . | P | Power | kW |
| b | Dedendum | mm | . . . . | R | Overall reduction | - |
| C | Centre distance | mm | . . . . | T | Teeth number in gear | - |
| D | Diameter of pitch circle | mm | . . . . | v | velocity | m/s |
| f | Facewidth | mm | . . . . | Y | Lewis form factor | - |
| F | Force | kN | . . . . | pa | Pressure angle | deg |
| K | Velocity factor | - | . . . . | ha | Helix angle | deg |
| n | Rotational speed | rpm | . . . . | st | Stress(direct) | N/mm2 |
| p | Circular pitch | mm | . . . . | m | Module (D/T) | mm |
Suffices: a axial s separating t tangential p pinion w wheel