Crank Torque to Wheel Torque Calculator

Calculator

Crank Torque

Input Torque Unit

Transmission Gear Ratio

Final Drive Ratio

Transfer Or Reduction Ratio

Drivetrain Efficiency (%)

Driven Wheels

Tire Rolling Radius

Radius Unit

Output Torque Unit

Formula Used

Overall Ratio = Gear Ratio × Final Drive Ratio × Transfer Ratio

Ideal Wheel Torque = Crank Torque × Overall Ratio

Total Wheel Torque = Ideal Wheel Torque × Drivetrain Efficiency

Torque Per Driven Wheel = Total Wheel Torque ÷ Driven Wheels

Tractive Force = Total Wheel Torque ÷ Tire Rolling Radius

Use decimal efficiency in the formula. For example, 88% becomes 0.88.

How to Use This Calculator

Enter crank torque from an engine dyno, catalog, or estimate.
Select the input torque unit.
Enter the active transmission gear ratio.
Enter the final drive ratio.
Use 1.00 for transfer ratio if no extra reduction exists.
Enter estimated drivetrain efficiency.
Enter driven wheel count and tire rolling radius.
Click the calculate button.
Use CSV or PDF export for saving results.

Example Data Table

Crank Torque	Gear Ratio	Final Drive	Efficiency	Driven Wheels	Tire Radius	Total Wheel Torque	Tractive Force
350 Nm	3.50	3.73	88%	2	0.34 m	4,019.40 Nm	11,821.76 N
420 Nm	2.10	4.10	90%	4	0.36 m	3,254.58 Nm	9,040.50 N
260 lb-ft	3.80	3.90	86%	2	13.5 in	4,493.44 Nm	13,107.17 N

Understanding Wheel Torque Conversion

Crank torque describes twisting force at the engine crankshaft. Wheel torque describes twisting force after gearing and drivetrain losses. The two values are related, but they are not equal. Gear multiplication can greatly raise torque before it reaches the driven tires.

Why Ratios Matter

Each ratio changes the torque path. A low transmission gear uses a high gear ratio. It gives strong launch force. A final drive ratio multiplies torque again. A transfer case or reduction box can add another multiplier. The calculator combines these ratios into one overall ratio. This makes the result easier to compare.

Efficiency and Real Output

No drivetrain transfers power perfectly. Bearings, gears, fluid drag, shafts, chains, and tires absorb energy. Efficiency represents the percentage that remains after these losses. A higher efficiency gives a higher wheel torque. A lower efficiency shows more torque loss. This is useful when comparing manual, automatic, chain, belt, and all wheel drive layouts.

Tire Radius and Force

Wheel torque becomes useful when it pushes against the ground. The tire rolling radius converts torque into tractive force. A smaller tire radius gives more force for the same wheel torque. A larger tire radius lowers force, but it may support higher road speed. That is why tire changes can affect acceleration feel.

Per Wheel Results

Total wheel torque is divided across driven wheels. A two wheel drive car sends torque to two tires. A four wheel drive vehicle may spread it across four tires. The split may not be perfectly equal in real systems, but this estimate is practical for planning.

Best Uses

Use this tool for gearing comparisons, drivetrain swaps, tire changes, and setup planning. It helps show why one gear feels strong and another feels relaxed. It also explains why drivetrain loss matters. The result is an estimate, not a dyno reading. Tire slip, converter multiplication, clutch behavior, traction control, and differential bias can change real performance. Still, the method gives a clear baseline for quick decisions.

Practical Accuracy

Enter realistic ratios from service manuals or verified gear charts. Use rolling radius under load, not unloaded diameter. When data is uncertain, compare several cases. Sensitivity checks quickly reveal which input changes the answer during setup.

FAQs

What is crank torque?

Crank torque is the turning force measured at the engine crankshaft. It is usually listed by engine dynos, manufacturer sheets, or performance estimates before drivetrain multiplication and losses.

What is wheel torque?

Wheel torque is the torque available at the driven wheels after gear multiplication, final drive multiplication, transfer reduction, and drivetrain efficiency losses.

Why is wheel torque higher than crank torque?

Wheel torque is often higher because transmission and final drive ratios multiply crank torque. Lower gears create stronger multiplication, which helps launch and low speed acceleration.

What efficiency value should I use?

Use 85% to 92% for many street drivetrains. Manual layouts may be higher. Automatic, all wheel drive, chain, or older drivetrains may be lower.

Should I use tire radius or diameter?

Use tire rolling radius. It is half the loaded rolling diameter. Loaded radius is better than unloaded tire size because real tires compress under vehicle weight.

Does this calculator include tire slip?

No. It estimates mechanical torque and force. Tire slip, traction limits, road surface, differential behavior, and traction control can change real acceleration.

Can I compare different gears?

Yes. Change the transmission gear ratio and calculate again. Lower gears usually produce more wheel torque, while higher gears reduce torque multiplication.

Can this estimate dyno wheel torque?

It gives a useful estimate, but it is not a dyno replacement. Real dyno readings depend on tires, rollers, temperature, calibration, drivetrain behavior, and measurement method.