How to use this calculator
Replace the example values with your own measurements or specifications. Keep the units shown beside each label. Results update as you type; reset restores the example.
Assumes no clutch or torque-converter slip and uses nominal tire diameter. Real rolling circumference, converter operation, or a CVT can make dashboard RPM differ.
The formula
A worked example
At 60 mph with a 26-inch tire, 0.75 top gear, and 3.73 final drive, estimated engine speed is about 2,170 rpm.
Common questions
What does an overdrive ratio below 1 mean?
The transmission output turns faster than its input, reducing engine speed for a given final drive and road speed.
Does this predict top speed?
No. It relates speed and RPM geometrically; available power, drag, limits, and traction are not modeled.
Sources & calculation method
This tool uses the geometric or dimensional relationship shown above. Conversion constants and units are stated in the formula or explanation so the calculation can be reproduced.
Prepared with AI assistance. Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.