Finding RPM with Gear Ratio, Speed, and Tire Size

Columns with a grey background are output.
Fill in all other columns and click the "Calculate" button to use.
OD is your transmission's overdrive ratio. If you do not have overdrive, use "1". If you have overdrive, but don't know the ratio, a good guess is ".7".

Gear
Ratio		 Speed
(MPH)		 OD
(see above)		 Tire
Diam. (in)		 RPM
Alternatively, you may use this calculator if you don't know your tire diameter. Instead, enter the 3 numbers listed on the side of the tire. For example, if the tire says something like "225/50/R16", use 225 for tire width, 50 for aspect ratio, and 16 for rim diameter.

Gear
Ratio		 Speed
(MPH)		 OD
(see above)		 Tire Width
(mm)		 Aspect
Ratio		 Diameter of
rim (in)		 RPM


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