Gear Ratio / RPM / Speed Calculator

Determine Speed
 Stock Tire Size: width (mm): profile (%): diameter (in): circumference (in): adjustment (%): Adjusted circ. (in):
 Engine Speed: RPM: Gear Ratio: Gear Ratio: Final Drive: Final drive:

Speed (mph) is:

Determine RPM
 Stock Tire Size: width (mm): profile (%): diameter (in): circumference (in): adjustment (%): Adjusted circ. (in):
 Wheel Speed: Speed (mph): Gear Ratio: Gear Ratio: Final Drive: Final drive:

RPM is:

Determine Ratio
 Stock Tire Size: width (mm): profile (%): diameter (in): circumference (in): adjustment (%): Adjusted circ. (in):
 Wheel Speed: Speed (mph): Engine Speed: RPM: Final Drive: Final drive:

Gear Ratio is:

Determine Speed: Use this calculator when you know your gearing and want to find your Speed at a given RPM

Determine RPM: Use this calculator when you know your gearing and want to find your RPM at a given speed

Determine Ratio: Use this calculator when you know your final drive, but want to find your Gear Ratio for a given RPM & speed.

Note: The circumference of the tire is computed for an ideal circle for the given tire dimensions.
You can use the "adjustment (%)" to raise or lower this by a percentage as you see appropriate

 B5 S4 6-speed gearing is: VW 1.8T trannys coded:EBQ, EMT, EGX, FBW Gear Ratios: Manual (Automatic) Manual 1st 3.500:1 (3.665:1) 3.300 2nd 1.889:1 (1.999:1) 1.944 3rd 1.231:1 (1.407:1) 1.308 4th 0.967:1 (1.000:1) 1.029 5th 0.806:1 (0.742:1) 0.837 6th 0.684:1 (----) Reverse 3.455:1 (4.096:1) Final Drive 4.111:1 (3.511:1) 3.938

The above is the S4 (6-speed manual) gearing (RPM vs Speed) per data logging using APR's ECU Explorer.  The bold areas are the actual datapoints logged, whereas the thin lines is the linear trendline with 0-intercept.