How to use this calculator
- Choose module or DP. Pick the size system your drawing or cutter uses, then enter the module or diametral pitch.
- Set pressure angle and teeth. Use the mating gear pressure angle and enter the number of teeth on the generated gear.
- Enter a mate if needed. Add a mating tooth count to calculate center distance.
- Adjust profile shift. Use positive profile shift if the undercut warning appears on low tooth counts.
- Download the profile. Check the live preview and click Download DXF for the generated gear outline.
How it works
This generator builds a standard full-depth involute spur gear. The pitch diameter is
d = m · z
where m is module and z is tooth count. The base circle is
d_b = d·cos α, and each tooth flank is traced as an involute from that
base circle. The generated outline is then repeated around the gear and exported as
a closed DXF polyline.
For imperial drawings, diametral pitch is converted to module with
m = 25.4 / DP. The same generated geometry drives the pitch, base, tip
and root diameters, the live preview and the DXF export, so there is no drift between
the numbers and the downloaded profile. For the sizing background, see
gear module vs diametral pitch
and involute gear geometry.
Once the profile is generated, the usual next checks are mesh compatibility and load. Use the involute gear calculator for a fuller geometry readout, the gear ratio calculator for speed and torque, and the gear mesh force calculator before sizing shafts or bearings.
Worked example
Verified against the live calculator
Generate a module-2, 20° spur gear with 20 teeth and a 40-tooth mate. The generator returns a 40 mm pitch diameter, 44 mm outside diameter, 35 mm root diameter and 60 mm center distance. The preview shows the full 20-tooth outline, and the DXF button downloads that same involute profile.
Reference data
Preferred metric modules help keep generated gears compatible with standard cutters, stock gears and replacements. The generator also accepts diametral pitch when you are working from an imperial drawing.
| Module (mm) | Circular pitch (mm) | ≈ Diametral pitch (1/in) | Notes |
|---|---|---|---|
| 1 | 3.142 | 25.4 | Fine-pitch instruments and small mechanisms. |
| 1.25 | 3.927 | 20.3 | |
| 1.5 | 4.712 | 16.9 | |
| 2 | 6.283 | 12.7 | Common general-machinery module. |
| 2.5 | 7.854 | 10.2 | |
| 3 | 9.425 | 8.47 | |
| 4 | 12.57 | 6.35 | |
| 5 | 15.71 | 5.08 | |
| 6 | 18.85 | 4.23 | |
| 8 | 25.13 | 3.18 | |
| 10 | 31.42 | 2.54 | Heavy power transmission. |
| 12 | 37.7 | 2.12 | |
| 16 | 50.27 | 1.59 | |
| 20 | 62.83 | 1.27 |
Source: ISO 54 preferred-module series. Diametral pitch shown for reference; DP gears use their own standard series.
Frequently asked questions
What does this gear generator export?
It exports the generated involute spur gear as a closed DXF polyline. The same geometry also renders in the live preview, so the profile you see is the profile you download.
Is this a real involute gear profile?
Yes. The tooth flanks are generated from the involute of the base circle. The calculator also returns pitch, base, tip and root diameters, tooth thickness, backlash and an undercut check.
Can I use module or diametral pitch?
Yes. Choose module for metric gears or diametral pitch for imperial gears. The generator converts DP to module internally with m = 25.4 / DP so the same geometry engine is used.
What pressure angle should I use for generated gears?
Use 20° unless you have a reason not to. It is the modern default for spur gears. Mating gears must use the same module or DP and the same pressure angle.
Does the DXF include a root fillet?
The DXF uses a geometric involute with a simplified root transition. It is good for layout, laser/waterjet/CAM starting geometry and educational work, but production gears should be checked against the manufacturing process and cutter geometry.
Method & assumptions
- External spur gear only; internal gears, racks, bevel gears and helical gears need different geometry.
- Standard full-depth tooth proportions: addendum = m and dedendum = 1.25m.
- Profile-shifted center distance assumes the mating gear is unshifted.
- The generated DXF uses a simplified root transition; verify cutter path, backlash, strength and tolerances before production use.
- For load-bearing gears, follow the profile export with mesh-force, shaft and bearing checks rather than treating the DXF as a complete design approval.