Result
Formula used
Wheel torque: T = F × r
Tractive effort: F = T ÷ r
Effective radius: r = T ÷ F
Wheel torque from shaft torque: Twheel = Tshaft × G × D × η
Shaft torque: Tshaft = Twheel ÷ (G × D × η)
How to use this calculator
Select the calculation mode first. Enter tractive effort, torque, or radius as required. Choose matching units beside each input. Add the transmission ratio, final drive ratio, and drivetrain efficiency when drivetrain analysis matters. Enter the number of driven wheels to estimate torque or effort per wheel. Choose an output torque unit and preferred decimal precision. Press Calculate to view the main answer and supporting drivetrain values. The result area also shows converted quantities and useful mechanical relationships.
Understanding tractive effort and torque
Tractive effort is the linear force available at the tire contact patch. Torque is the rotational turning effect applied around an axis. Wheel radius links both quantities through a simple mechanical relationship. A larger wheel needs more torque for the same tractive effort. A smaller wheel creates more tractive effort from identical wheel torque.
Why gearing matters
Transmission and final drive ratios multiply shaft torque before it reaches the wheels. Real drivetrains also lose some energy through gears, bearings, joints, and tires. Efficiency accounts for part of this loss. Higher overall gearing increases wheel torque while reducing wheel speed for a given engine speed.
Driven wheels and load sharing
Total tractive effort may be shared by several driven wheels. Dividing total force by the driven wheel count gives an idealized per-wheel value. Real vehicles rarely share force perfectly because tire loading and differential behavior vary. The calculator therefore treats equal sharing as a convenient engineering estimate.
Reverse calculations
The tool can solve several related problems. It can find torque from force and radius. It can find force from torque and radius. It can solve for radius when force and torque are known. It can also estimate the required transmission ratio from target wheel torque, shaft torque, final drive ratio, and efficiency.
Practical interpretation
Tractive effort is useful for acceleration, grade climbing, towing, and traction analysis. Wheel torque alone cannot describe vehicle acceleration because wheel radius and available tire grip also matter. Calculated values should therefore be compared with tire limits, vehicle mass, road grade, and operating conditions. Use realistic effective rolling radius rather than unloaded tire radius. This improves results during normal vehicle operation significantly.
Example tractive effort and torque table
| Tractive effort | Effective radius | Wheel torque | Example context |
|---|---|---|---|
| 1,500 N | 0.25 m | 375 N·m | Light utility drive |
| 3,000 N | 0.30 m | 900 N·m | Small passenger vehicle |
| 5,000 N | 0.32 m | 1,600 N·m | Higher launch force |
| 10,000 N | 0.40 m | 4,000 N·m | Heavy vehicle application |
| 20,000 N | 0.50 m | 10,000 N·m | Industrial or off-road drive |
Frequently asked questions
What is tractive effort?
Tractive effort is the forward force produced at the driven wheel contact patch.
How is torque calculated from tractive effort?
Multiply tractive effort by the effective wheel radius after converting both values to consistent SI units.
Should I use tire radius or rolling radius?
Effective rolling radius is usually better because loaded tires deform during normal operation.
How does gear ratio affect wheel torque?
Higher overall reduction multiplies wheel torque but reduces wheel speed relative to shaft speed.
Why include drivetrain efficiency?
Efficiency estimates mechanical losses between the driving shaft and the wheels.
Can this calculator find required gear ratio?
Yes. Choose the gear ratio mode and provide target wheel torque, shaft torque, final drive ratio, and efficiency.
Does the number of driven wheels change total torque?
It changes the idealized torque or force per wheel, but total system demand remains tied to overall tractive effort.