Calculator
Gear Speed Calculator
Work out road speed in any gear from engine rpm, gear ratio, final drive and tyre size — including speed per 1,000 rpm and the speed at the redline in each gear.
282.8 km/hroad speed
175.7 mphroad speed
40.4 km/hper 1,000 rpm
2,222wheel rpm
The car does 283 km/h (176 mph) at 7,000 rpm in this gear.
Speed across the rev range
| rpm | km/h | mph |
|---|---|---|
| 1,000 | 40.4 | 25.1 |
| 2,000 | 80.8 | 50.2 |
| 3,000 | 121.2 | 75.3 |
| 4,000 | 161.6 | 100.4 |
| 5,000 | 202.0 | 125.5 |
| 6,000 | 242.4 | 150.6 |
| 7,000 | 282.8 | 175.7 |
| 8,000 | 323.2 | 200.8 |
How the calculation works
The gearbox ratio and the final drive (differential) both reduce engine speed before it reaches the wheels: wheel rpm = engine rpm ÷ (gear ratio × final drive). Multiply by the tyre's rolling circumference and you have road speed. Ratios below 1.0 are overdrive gears — the wheels turn faster than the gearbox input.
Where to find the numbers
- Gear ratios and final drive are listed in the manufacturer's technical data or the gearbox code's spec sheet.
- For a dual-clutch with two final drives, use the final drive that serves the gear you are calculating.
- Real speed is slightly higher at high speed as the tyre grows, and lower with an automatic's torque converter slipping.
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