Free tool
Gear ratio & speed calculator
Enter your tire size, gearbox ratios, final drive and redline. The calculator shows the speed each gear reaches at redline, where the engine lands after every upshift, and the RPM at any road speed.
Tire size
Tire diameter 653 mm (25.7 in), circumference 2.052 m.
RPM vs speed, each gear to redline
| Gear | Ratio | Top at redline | RPM after upshift |
|---|---|---|---|
| 1 | 3.36 | 45 mph | 4559 (−2841) |
| 2 | 2.07 | 73 mph | 5112 (−2288) |
| 3 | 1.43 | 106 mph | 5175 (−2225) |
| 4 | 1.00 | 152 mph | 6216 (−1184) |
| 5 | 0.84 | 181 mph | 4933 (−2467) |
| 6 | 0.56 | 271 mph | — |
1: 131052: 80743: 55774: 39005: 32766: 2184
How it works
- 1Tire diameter = rim diameter + 2 × sidewall height, where sidewall = width × aspect ratio.
- 2Wheel RPM = engine RPM ÷ (gear ratio × final drive).
- 3Speed = wheel RPM × tire circumference. Real tires grow slightly at speed and squash under load, so expect a few percent of difference.
FAQ
What does a shorter final drive do?
A numerically higher final drive (for example 4.10 instead of 3.73) gives more acceleration in every gear and lower top speed per gear, and keeps the engine at higher RPM.
Why does RPM drop after a shift matter?
If the drop lands the engine below its power band, the car bogs out of corners. Gearing that keeps each shift inside the power band is faster.