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Gear Speed Calculator
Your exact gearing, decoded: speed at redline in every gear, cruise rpm at 100 km/h, and what a final drive or tire change would really do — before you buy the parts.
Gearing · v1.0
Defaults: a typical FR coupe- Speed at redline, per gear59 / 97 / 138 / 175 / 213 / 277
- Theoretical top speed277 km/h
- Tire circumference1.965 m
Top speed shown is gearing-limited. Real cars usually hit the aerodynamic wall first.
How gearing math works
Every gear is just a multiplication. Engine rpm divided by the gear ratio, divided again by the final drive, gives wheel rpm; multiply by tire circumference and you have road speed. That one chain explains cruise rpm, redline speeds and why two mods people love — bigger tires and shorter final drives — pull in exactly opposite directions.
Use it before money changes hands: type your current setup, then try the new final drive or tire size and watch cruise rpm and per-gear speeds move. Thirty seconds here beats discovering your motorway cruise turned into 3,400 rpm the hard way.
What changes what
| Change | Acceleration | Cruise rpm | Top speed (geared) |
|---|---|---|---|
| Shorter final drive (higher number) | Stronger | Higher | Lower |
| Taller final drive (lower number) | Weaker | Lower | Higher |
| Larger tire diameter | Weaker | Lower | Higher |
| Smaller tire diameter | Stronger | Higher | Lower |
FAQ
The owner's manual, the manufacturer's technical specs, or any reputable spec database for your exact model and gearbox code. Ratios differ between years and gearbox options, so match the code.
The calculator shows the gearing-limited speed at redline. Real cars are usually drag-limited: aero drag grows with the square of speed, and the engine runs out of power before the gearing runs out of road.
A numerically higher final drive multiplies wheel torque in every gear — stronger acceleration, but higher rpm at any road speed, louder cruising and slightly higher fuel use. Bigger tires do the exact opposite.