Free Spur Gear Center Distance Calculator
Calculate pitch diameters, theoretical & operating center distances, outside tip diameters, and recommended backlash for spur gear trains.
⚙️ Gear Standard & Tooth Counts
e.g. 12, 16, 20, 24, 32 DP
e.g. 1.0, 1.5, 2.0, 2.5 mm
Driver gear
Driven gear
📊 Pitch Diameters & Center Distance
Center Distance (C)
0.0000"
0.00 mm shaft-to-shaft
Gear Ratio
3.00 : 1
3.00x reduction
Pinion Pitch Dia (D1)
0.000"
Tip OD: 0.000"
Gear Pitch Dia (D2)
0.000"
Tip OD: 0.000"
Operating Center Distance with Backlash:
0.0000"
Tooth Whole Depth:
0.000"
Pinion Undercut Warning:
No Undercutting (≥17 teeth)
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Frequently Asked Questions
What is the formula for spur gear pitch diameter?
For Imperial Diametral Pitch: Pitch Diameter = Teeth / DP. For Metric Module: Pitch Diameter = Module × Teeth.
How do you calculate the outside tip diameter of a spur gear?
Outside Diameter = (Teeth + 2) / DP in Imperial, or Module × (Teeth + 2) in Metric.
What is the minimum number of teeth to avoid undercutting in a 20° gear?
For a standard full-depth 20° pressure angle spur gear, the theoretical minimum number of teeth to avoid undercutting is 17 teeth.
How much does changing center distance affect the gear ratio?
Involute gear teeth possess a unique property: changing the center distance slightly does NOT change the gear velocity ratio. However, it changes operating backlash and operating pressure angle.