Transmission Gear Ratio & Speed Calculator
Calculate vehicle speed by gear and RPM. Includes a massive database of transmission ratios (Tremec, ZF, Honda, etc.) and tire size simulation.
1. Select Transmission
2. Vehicle Specs
3. Tire Size
Gear Ratios
Theoretical Max Speeds (MPH)
About
Optimizing a vehicle for track performance or highway efficiency requires a deep understanding of gearing. This tool calculates the theoretical top speed in each gear based on engine RPM, tire diameter, transmission gear ratios, and the final drive ratio. It is essential for tuners selecting the right differential swap or verifying if a specific gearbox allows the engine to stay in the power band.
The calculator accounts for the mechanical relationship where engine speed is reduced (torque multiplication) through the transmission and differential before reaching the wheels. Understanding shift points helps in minimizing RPM drop during upshifts, ensuring maximum acceleration.
Formulas
The speed of the vehicle (v) is calculated as:
Where Ctire is the tire circumference and K is a unit conversion constant (1056 for mph, 16666.7 for km/h).
Reference Data
| Transmission | 1st Gear | 2nd Gear | 3rd Gear | 4th Gear | 5th Gear | 6th Gear |
|---|---|---|---|---|---|---|
| Tremec T56 (F-Body) | 2.66 | 1.78 | 1.30 | 1.00 | 0.74 | 0.50 |
| ZF 8HP70 (BMW) | 4.71 | 3.14 | 2.10 | 1.67 | 1.29 | 1.00 |
| Getrag V160 (Supra) | 3.82 | 2.36 | 1.68 | 1.31 | 1.00 | 0.79 |
| Honda S80 (Integra R) | 3.23 | 2.10 | 1.45 | 1.10 | 0.84 | - |
| Subaru STI 6MT | 3.63 | 2.23 | 1.52 | 1.13 | 0.97 | 0.75 |
| Ford MT82 (Mustang) | 3.66 | 2.43 | 1.69 | 1.32 | 1.00 | 0.65 |
| Porsche PDK (991) | 3.91 | 2.29 | 1.58 | 1.18 | 0.94 | 0.79 |
| Mazda CD4E | 2.88 | 1.57 | 1.00 | 0.70 | - | - |