Autocross Speed-in-Gears Calculator

Select a car from the pre-defined list or enter/adjust the values below then click "Calculate!"

Tire Width
Aspect Ratio
Wheel Size
Tire Diameter
Use Tire Diameter
First Gear
Second Gear
Third gear
Fourth Gear
Fifth Gear
Sixth Gear
Seventh Gear
Eighth Gear
Ninth Gear
Tenth Gear
Final Drive
RPM Step
Use Fudge* (.965)

*A "fudge factor" is applied by default to account for the slight non-roundness of tires in contact with the ground. You can disable this by de-selecting the "Use Fudge" check box.

Don't see your favorite car in the pre-defined list? Send me the data!

As much as I'd love to keep this calculator always up-to-date with new (and old) car information, I'm only one person and there are only 24 hours in the day.

If you don't find your favorite car in the pre-defined data list (or if you find an error!), send me the info and I'll make the update.

I need several pieces of information to add a car to the list:

Note: For cars with multiple final drive ratios, be sure to specify which gears use which ratio.

Send all of this data via email to with the subject line "Speed in Gears data".

Thanks for your support!