Gear Speed Calculator
RPM and gearing to mph (and back) from tire size.
Direction
- Overall gear ratio: 13.055
- Estimated speed: 14.2 mph
What is this tool?
Road speed follows from engine RPM, overall gear reduction (transmission × final drive), and tire revolutions per mile. This tool uses the nominal tire size diameter to estimate revs/mile, then converts RPM→speed or speed→RPM for gearing what-ifs.
How to use it
- Enter tire size (e.g. 225/45R17), gear ratio, and final drive.
- Choose RPM→speed or speed→RPM.
- Enter RPM or target mph to see the result.
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