How to use this calculator
Enter the wheel-side torque for your scenario in newton-meters. Select the radius unit and enter the effective rolling radius. Read ideal force in newtons or kilonewtons. Keep the torque basis consistent: do not enter total axle torque and then multiply the result by the number of wheels. The defaults are hypothetical, not a vehicle specification.
This is an ideal torque-to-force relationship. It does not model tire slip, the traction limit, wheel rotational acceleration, braking or drivetrain losses upstream of the entered wheel torque. Rolling resistance, drag and grade are not subtracted. The result is not net force, a towing rating, available grip or a prediction of 0–60 time. A nominal tire-size radius is only an approximation to the effective radius needed by this model.
The formula
A worked example
For 1,200 N·m of total torque at equal-radius driven wheels and a 0.30 m effective rolling radius, F = 1,200 ÷ 0.30 = 4,000 N = 4 kN. If two wheels each receive 600 N·m, each contributes 2,000 N in this ideal model, still totaling 4,000 N. Keeping torque at 1,200 N·m while increasing radius to 0.40 m reduces ideal force to 3,000 N.
Effect of radius at unchanged wheel torque
Original hypothetical examples, each using 1,200 N·m of wheel-side torque. No traction limit applied.
| Effective radius (m) | Ideal force (N) | Ideal force (kN) |
|---|---|---|
| 0.25 | 4,800 | 4.8 |
| 0.30 | 4,000 | 4.0 |
| 0.40 | 3,000 | 3.0 |
| 0.50 | 2,400 | 2.4 |
Common questions
Can I enter engine torque directly?
No. Gear ratios and drivetrain losses affect the torque reaching the wheels. Supply wheel-side torque for the operating point you want to study. This tool does not silently estimate a transmission ratio, final drive ratio or efficiency.
Should I multiply by two for a two-wheel-drive car?
Only sum separately calculated forces when your inputs describe individual wheels. If you enter the combined torque at both driven wheels and they share the same effective radius, the result is already their combined ideal force. Multiplying it by two would double-count.
What if driven wheels have different radii?
Calculate each wheel separately with its own torque and effective radius, then add the forces for the same direction of drive. A single common-radius calculation cannot represent different radii accurately. Torque distribution is an input assumption, not something this tool predicts.
Why does a larger radius reduce force?
At fixed wheel torque, force is inversely proportional to radius. A 0.40 m radius produces three quarters of the force obtained at 0.30 m. This comparison holds wheel torque fixed; it does not account for an engine moving to another operating speed.
Is the result limited by tire grip?
No. The formula can return more force than the tires can transmit. Tire-road behavior and wheel dynamics require additional inputs and models. Treat the number as the ideal force associated with the entered torque, not proof that a vehicle can apply it.
Can I divide the result by mass to get acceleration?
Not as a complete vehicle prediction. Acceleration depends on net external force and inertia. This tool has not subtracted road loads or resolved traction and rotating components. Use the separate acceleration calculator to summarize an observed speed change over time.
Does wheel diameter mean rim diameter?
No. This tool asks for an effective tire rolling radius. Rim diameter describes only the wheel rim, and tire diameter is twice a geometric tire radius. Neither is automatically the effective rolling radius of a loaded tire. Check the basis of your measurement or specification.
What does zero torque mean here?
Zero entered drive torque gives zero ideal drive force. It does not imply that the vehicle has stopped or that total force is zero: braking, gravity, drag and other forces are outside this calculation.
Sources & calculation method
MathWorks: Longitudinal Vehicle uses axle torque divided by rolling radius as the drive-force component in an ideal longitudinal model, separately from braking and road resistance. This calculator isolates that relationship; it does not implement the full vehicle model. Examples are original arithmetic, not road tests.
Explore resistance separately with the Rolling Resistance Calculator and Aerodynamic Drag Power Calculator. The Gear Ratio RPM Calculator handles speed geometry, while the Vehicle Acceleration Calculator summarizes a measured speed interval.
Reference accessed September 30, 2026. The source does not endorse the site or independently review this calculator.
Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.