Gear Module and Centre Distance Calculator
Pitch diameter, outside diameter, circular pitch and the centre distance of a gear pair.
Results
Pitch diameter
80.000
mm
Outside diameter
84.000
mm
Distance
60.000
mm
Thread pitch
6.2832
mm
What this tool does
The module is the single number that decides whether two gears will mesh: same module, and any tooth counts work together. Pitch diameter is module times teeth, the blank is two modules larger, and the centre distance is simply the average of the two pitch diameters.
Formula
d = m × z , dₐ = m × (z + 2)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
m | Module | mm |
z | Number of teeth | — |
z2 | Number of teeth | — |
D | Pitch diameter | mm |
DA | Outside diameter | mm |
CD | Distance | mm |
P | Thread pitch | mm |
Worked example
- Module2 mm
- Number of teeth40
- Number of teeth20
- Pitch diameter80.000 mm
- Outside diameter84.000 mm
- Distance60.000 mm
- Thread pitch6.2832 mm
Limitations
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.