Gear Ratio Calculator US

RPM Calculator

Gear Ratio
Tire Height
5 Speed

Gear ratio for new tire size

New Tire Diameter:
Old Tire Diameter:
Current Gear Ratio:
New Gear Ratio:
Round down to nearest actual ratio

Transmission Final Gear Ratio

Ring Gear and Pinion Ratio
ex: 4.10
Tire Height
ex: 35
Transmission Final Gear Ratio
ex: 2.54
Engine RPM

* auto = D in an AOD (1:1)
* AOD is calculated at .70 transmission ratio
* 5 speed is calculated at .80 transmission ratio
* Many late model vehicles have a taller overdrive ratio, such as Toyota Tacoma & Tundra with 6 speed Auto have a .58:1 overdrive.
Use 1:1 RPM x .58 = RPM

This table represents the recommended RPM range @ 60mph.
Note: When you enter the desired gear ratio, new tire height and 60mph into the calculator on the left, the RPM range for your vehicle should fall between the values below.
Example: If you have a 6 cyl vehicle with an Auto transmission without overdrive your RPM's should fall between 2000-3000 at 60mph. If you have 35" tires with a 4.88 gear ratio your RPM range will fall between the desired 2000-3000 RPM's.
4 cyl2200-3200
6 cyl2000-3000
small block1800-2800
big block1600-2600
GM Duramax 6.2L1800-2800
Ford Powerstroke (non-turbo)1600-2500
Ford Powerstroke (turbo)1400-2200
Dodge Cummins Turbo Diesel1400-2200

This calculator requires the use of Javascript enabled and capable browsers.
These calculators are designed to give the approximate engine RPM (revolutions per minute) based on the ring gear and pinion gear ratio, the height of the tires (diameter from ground to top of the tire while mounted on the vehicle) and the transmission final gear ratio.

This calculator does not take into consideration any drive train loss, road and weather conditions or driver skills. The calculated results are displayed; the higher the engine RPM, the greater the potential speed at the cost of fuel, heat, friction and engine longevity. The results are only an estimate - your mileage may vary.