Involute Gear Calculator
SI
Imp
Imperial
Inputs
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Size system
Specify gear size by metric module (mm) or imperial diametral pitch (teeth per inch).
Module (metric)
Diametral pitch (imperial)
Module / DP
(m)
Module in mm (metric) or diametral pitch in 1/in (imperial), per the size system above.
mm
Pressure angle
(α)
Standard pressure angle. 20° is by far the most common.
14.5°
20°
25°
Tooth count
(z)
Number of teeth on this gear.
Mating tooth count
(z₂)
Teeth on the mating gear — used for center distance. Set 0 if none.
Profile shift
(x)
Profile-shift (addendum-modification) coefficient. Positive shifts the profile outward to avoid undercut.
Results
Default result
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Pitch diameter
(d)
40
mm
Also computed
Module (mm)
2
Diametral pitch (1/in)
12.7
Base diameter
(d_b)
37.59
mm
Outside (tip) diameter
(d_a)
44
mm
Root diameter
(d_f)
35
mm
Addendum
2
mm
Dedendum
2.5
mm
Whole depth
4.5
mm
Circular pitch
(p)
6.283
mm
Tooth thickness (at pitch)
(s)
3.142
mm
Center distance (with mate)
(a)
Pass
60
mm
Recommended backlash
0.08
mm
Typical 0.03–0.05 × module.
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Method notes
2 notes
Standard full-depth involute teeth (addendum = m, dedendum = 1.25 m, clearance = 0.25 m).
Minimum teeth to avoid undercut at 20° is 18 without profile shift.
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