Gear Ratio Calculator
Calculate overall gear ratio, RPM at speed, and speed at RPM from transmission gear ratio, differential ratio, and tire diameter.
Overall Gear Ratio
12.76:1
Speed at 3,000 RPM
18.2 mph
Speed (metric)
29.3 km/h
RPM at 60 mph
9,895
Tire Revs/Mile
776
๐ก How to Use the Gear Ratio Calculator
How Gear Ratios Work
The overall gear ratio determines how many times the engine turns for each wheel revolution. It's the product of the transmission gear ratio and the differential (axle) ratio.
Overall Ratio = Transmission Gear ร Differential Ratio
Speed (mph) = (RPM ร Tire Circumference) รท (Overall Ratio ร 63,360) ร 60
Speed (mph) = (RPM ร Tire Circumference) รท (Overall Ratio ร 63,360) ร 60
Lower (numerically higher) gears provide more torque multiplication for acceleration. Higher (numerically lower) gears allow cruising at lower RPM for fuel economy.
Typical Gear Ratios
| Gear | Typical Ratio | Purpose |
|---|---|---|
| 1st | 3.2โ4.5:1 | Launch, low-speed torque |
| 2nd | 1.8โ2.5:1 | Acceleration |
| 3rd | 1.2โ1.5:1 | Mid-range power |
| 4th | 1.0:1 (direct) | Cruising efficiency |
| 5th/6th | 0.65โ0.85:1 | Overdrive, highway fuel economy |