How to use this calculator
- Enter engine torque. Use crankshaft torque before drivetrain losses.
- Enter ratios. Enter transmission, final drive and transfer ratios.
- Set efficiency and tire radius. Apply a drivetrain efficiency estimate and rolling tire radius.
- Read wheel force. Review wheel torque and tire contact force.
How it works
Gearing multiplies torque and reduces speed. The calculator uses wheel torque = engine torque x gear x final x transfer x efficiency, then converts torque into tire contact force with force = wheel torque / tire radius.
Pair this with the vehicle speed calculator to see the road speed at the same gear, or with the brake torque calculator when comparing drive force with braking force.
Worked example
Verified against the live calculator
A 300 N*m engine in a 3.50 first gear with a 3.73 final drive and 90% efficiency makes about 3,520 N*m at the wheel. With a 330 mm tire radius, that is about 10.7 kN of tire contact force before traction limits.
Frequently asked questions
How do you calculate wheel torque?
Wheel torque is engine torque multiplied by transmission ratio, final drive ratio, transfer ratio and drivetrain efficiency.
How do you calculate tire contact force?
Tire contact force is wheel torque divided by tire rolling radius.
Does this predict acceleration?
No. Acceleration also needs vehicle mass, traction, weight transfer, aerodynamic drag, rolling resistance and shift behavior.
What drivetrain efficiency should I use?
Use measured data when possible. As a screen, manual drivetrains are often estimated around 85-95%, while automatic or AWD systems can be lower depending on layout.
Method & assumptions
- Torque is idealized steady torque after the entered efficiency allowance.
- Actual force is limited by tire grip, traction control, clutch/converter behavior and drivetrain strength.