Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Single selected gear. Effective rolling diameter, not nominal rim diameter, is required.
Example Calculation
- Chainring teeth: 48
- Sprocket teeth: 16
- Effective wheel diameter: 27 in
48/16 gearing has ratio 3; a 27-inch wheel gives 81 gear inches.
Frequently asked questions
How do I use this calculator?
Enter chainring teeth, sprocket teeth, effective wheel diameter. The result updates automatically. Use Reset to restore the example values.
What method does it use?
ratio=front/rear; gear inches=wheel diameter × ratio.. Single selected gear. Effective rolling diameter, not nominal rim diameter, is required.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.