Speed at Engine RPM Calculator
Find road speed at a set engine RPM. Use the calculator below. Results update as you type.
Wheel RPM = (Speed in MPH × 63,360) / (Circumference in inches × 60)How the Speed at Engine RPM Calculator Works
This calculator works by dividing engine RPM by the axle and gear ratios to get wheel RPM, then converting wheel RPM into road speed. It answers how fast the vehicle goes at a chosen engine speed.
- Enter the engine RPM, for example 2,000.
- Enter the axle ratio (3.73) and gear ratio (0.69).
- Enter the tire diameter, for example 33 in.
- Read the speed: 76.3 mph (122.8 km/h).
The Formula
The formula is Speed (mph) = (Engine RPM × Diameter in inches) ÷ (Axle Ratio × Gear Ratio × 336.13).
Wheel RPM = Engine RPM ÷ (Axle × Gear) Speed (mph) = Wheel RPM × Circumference (in) × 60 ÷ 63,360 Speed (mph) = (Engine RPM × Diameter) ÷ (Axle × Gear × 336.13)Worked example: (3,000 × 31) ÷ (3.73 × 0.69 × 336.13) = 107.5 mph (173.0 km/h).
Conversion Table
The conversion table shows road speed at 7 engine speeds for 4 tire diameters, with a 3.73 axle and 0.69 top gear. Speeds at high RPM are theoretical; drag and engine output limit the real top speed.
At 2,000 RPM, moving from a 29 in to a 35 in tire raises cruise speed from 67.0 mph to 80.9 mph.
| Engine RPM | 29 in Tire | 31 in Tire | 33 in Tire | 35 in Tire |
|---|---|---|---|---|
| 1500 | 50.3 | 53.8 | 57.2 | 60.7 |
| 2000 | 67.0 | 71.7 | 76.3 | 80.9 |
| 2500 | 83.8 | 89.6 | 95.4 | 101.1 |
| 3000 | 100.6 | 107.5 | 114.4 | 121.4 |
| 3500 | 117.3 | 125.4 | 133.5 | 141.6 |
| 4000 | 134.1 | 143.3 | 152.6 | 161.8 |
| 5000 | 167.6 | 179.2 | 190.7 | 202.3 |
What Is the Speed at Engine RPM Calculator?
The Speed at Engine RPM Calculator is a tool that converts engine speed into road speed for a given tire size and gearing. It is the reverse of the engine RPM calculator.
The tool helps match cruise speed to an engine's most efficient RPM range, and it predicts the speed at each shift point.
Common Uses
This calculator has 4 uses: efficiency cruising, shift-point speeds, rev-limiter speeds and gearing comparison.
- Cruise efficiently: Find speed at peak-torque RPM.
- Map shift points: See road speed at each shift RPM.
- Find limiter speeds: Compute theoretical speed at redline.
- Compare gearing: Test tire and axle combinations.