When to use this calculator
Find the tooth-count ratio of a simple gear pair. For a simple external gear pair, output speed magnitude is input speed divided by this ratio.
Explore the gears, belts & motion calculators for other questions in this topic. For a related calculation, use the Lead Screw Linear Speed Calculator: Translate screw rotation into ideal axial travel rate.
PUTTING IT INTO PRACTICE
Gear Ratio: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Driven gear teeth (integer) | 60 |
| Driving gear teeth (integer) | 20 |
| Result | 3 × |
- Check the input labels and enter the example values above.
- Apply the relationship: Driven/driving ratio = driven teeth/driving teeth.
- The result is 3 ×, rounded for display.
How to interpret your result
For a simple external gear pair, output speed magnitude is input speed divided by this ratio.
Use compatible modules and effective pitch dimensions. No-slip and ideal-mesh assumptions omit losses and dynamics. A ratio calculation does not select a safe shaft, belt, bearing or gear rating.
Frequently asked questions
Why is a lead-screw lead different from its pitch?
Pitch is the axial distance between thread forms. A multi-start screw advances by pitch times the number of starts per revolution.
When is the gear ratio calculator useful?
Find the tooth-count ratio of a simple gear pair. For a simple external gear pair, output speed magnitude is input speed divided by this ratio.
How do I use the gear ratio calculator?
Enter driven gear teeth (integer), driving gear teeth (integer). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Driven/driving ratio = driven teeth/driving teeth.
What should I check before using the result?
For a simple external gear pair, output speed magnitude is input speed divided by this ratio.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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