Gear Train Calculator
Calculate the overall ratio and output speed of a multi-stage compound gear train.
How it works
- 1Enter the driver and driven tooth counts for each gear stage (up to 3 stages). Leave a stage blank to exclude it.
- 2The calculator multiplies each stage’s driven ÷ driver ratio together to get the overall gear-train ratio.
- 3Enter your input shaft speed (rpm) to see the final output speed after all reductions.
Use cases
- Designing a multi-stage gearbox to achieve a precise output speed from a fixed motor.
- Verifying that a compound drive train achieves the torque multiplication needed for a machine.
- Checking the cumulative ratio of a bicycle or automotive gear cluster.
Frequently asked questions
How does a gear train multiply ratios?
Each meshing pair of gears produces its own ratio (driven ÷ driver). In a gear train, the output of one stage drives the next, so the overall ratio is the product of every stage’s ratio. For example, two stages of 12→36 and 14→28 give (36÷12) × (28÷14) = 3 × 2 = 6 : 1 overall.
What does an overall ratio greater than 1 mean?
A ratio above 1 (e.g. 6 : 1) is an overall speed reduction — the output shaft turns slower than the input. The trade-off is that available torque is multiplied by the same factor, less drivetrain losses.
How is output speed calculated?
Output speed (rpm) = Input speed (rpm) ÷ Overall ratio. With a 6 : 1 ratio and 1500 rpm input, the output is 1500 ÷ 6 = 250 rpm.
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