Estimate crank torque from wheel torque precisely. Account for gearing, efficiency, and final drive losses. Review power, force, reduction, and losses in seconds confidently.
Total Reduction = Gear Ratio × Final Drive Ratio × Transfer Ratio
Effective Efficiency = (Drivetrain Efficiency ÷ 100) × (1 − Accessory Loss ÷ 100)
Crank Torque = Wheel Torque ÷ (Total Reduction × Effective Efficiency)
Wheel Force = Wheel Torque ÷ Wheel Radius
Angular Speed = 2π × RPM ÷ 60
Crank Power = Crank Torque × Angular Speed
The calculator converts units first. Then it applies gearing and losses. The torque result represents an estimated crankshaft requirement for the entered wheel torque.
| Wheel Torque (Nm) | Gear Ratio | Final Drive | Transfer Ratio | Efficiency (%) | Wheel Radius (m) | RPM | Estimated Crank Torque (Nm) | Estimated Power (kW) |
|---|---|---|---|---|---|---|---|---|
| 1800 | 3.20 | 4.10 | 1.00 | 88 | 0.31 | 3200 | 155.90 | 52.24 |
| 1500 | 2.66 | 3.73 | 1.00 | 90 | 0.32 | 2800 | 167.98 | 49.25 |
| 2200 | 3.80 | 4.56 | 1.00 | 85 | 0.34 | 3500 | 149.37 | 54.75 |
Wheel torque is the turning force available at the tire. Crank torque is the turning force produced by the engine. They are not equal. The drivetrain changes torque through gear multiplication and mechanical loss. Engineers use this relationship during powertrain sizing, traction studies, dyno comparisons, and performance validation. A good estimate helps you compare engine output with wheel demand. It also helps you understand how gearing changes the load path across shafts, gears, and tires.
The wheel sees torque after transmission multiplication. Final drive multiplication adds more torque. A transfer case can also change the result. Efficiency lowers the amount that reaches the wheel. To estimate crank torque from wheel torque, the calculator divides wheel torque by the total ratio and effective efficiency. This process moves backward through the drivetrain. The result shows the engine torque needed to support the entered wheel torque under the selected conditions.
Use the active gear ratio, not a nominal average. Use the real axle ratio. Include a transfer ratio for low range cases. Enter a realistic efficiency value. Manual systems often lose less than automatic systems under the same load. Tire radius matters because wheel force depends on it. Engine RPM adds power estimation. Accessory loss can model extra demand from pumps or driven components. Better inputs produce more useful crank torque estimates.
This calculation supports drivetrain design, motorsport setup, towing studies, and off-road analysis. It can also help with EV reduction ratio checks and hybrid system comparisons. Use it to compare measured wheel torque with expected engine torque. Use it to estimate shaft loading, launch behavior, and traction demand. The result is still an estimate. Real systems change with slip, temperature, tire growth, and transient load. Even so, this method remains fast, practical, and technically useful.
It estimates crankshaft torque from wheel torque. It works backward through gearing and losses. It also shows wheel force and optional power when RPM is entered.
Gear reduction multiplies torque at the wheel. That means a smaller engine torque can create a larger wheel torque. The calculator removes that multiplication to estimate crank torque.
Use a realistic full-path drivetrain efficiency. Many practical estimates fall between 80% and 92%. Use measured data when available. Keep the value conservative for planning work.
Tire size does not directly change the torque conversion formula. It does change wheel force. A larger effective radius lowers force for the same wheel torque.
Yes, when a transfer case or extra reduction stage is active. Leave it at 1.00 when no extra stage exists. This keeps the total reduction accurate.
Yes. Enter the measured wheel torque, active ratios, and a reasonable efficiency value. The output becomes an estimated crank torque, not a certified engine dyno value.
Accessory loss lets you model extra drag beyond the main drivetrain efficiency. Keep it at zero unless you specifically want to include added parasitic demand.
Yes. The same torque path logic applies to EVs, single-speed reducers, and many gearbox systems. Enter the correct reduction and efficiency values for the architecture.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.