Gear Ratio Calculator

Enter your ratios, final drive and tyre size to see road speed in every gear, where each shift lands, and how relaxed the car will be at a cruise.

Drivetrain

Start from

Loads a typical set you can then edit.

Gear ratios

Final drive

The differential ratio, after the gearbox.

Tyre size

Width / aspect ratio / rim diameter.

Redline rpm

Shift at rpm

Speed in every gear

Theoretical max

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Top gear at redline

Ratio spread

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First to top

Tyre diameter

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Overall

Rolling circumference

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Per wheel revolution

Gear by gear

Gear	Ratio	Overall	Shift at	Lands at	RPM @ 100	Step

These are geometric figures, not performance predictions

“Theoretical max” is simply the speed top gear reaches at redline. A real car runs out of power against aerodynamic drag well before that, so a road car usually tops out one gear earlier and well short of this number. Use the chart for spacing and the shift columns for setup; use the torque calculator for what the engine can actually push.