About the Final Drive Ratio Calculator
Overall drive ratio from gearbox and differential, with road speed at any engine RPM.
Also known as: differential ratio, axle ratio calculator, overall gearing, speed at rpm.
How to use this calculator
- Enter gearbox ratio, final drive / differential ratio, tyre rolling diameter, engine speed.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
overall ratio = gearbox ratio × final drive ratio
Worked example
Using the values pre-filled in the calculator above:
- Gearbox ratio = 1
- Final drive / differential ratio = 3.9
- Tyre rolling diameter = 640 mm
- Engine speed = 3,000 RPM
the calculator returns:
- Overall ratio: 3.9 : 1
- Road speed: 92.8 km/h
- In mph: 57.66
- Wheel speed: 769.2 RPM