How do I determine drive torque and power?

The decisive calculations for selecting the right motor for your screw jack. Once the gearbox size has been defined on the basis of load capacity, the drive torque and drive power are determined. These quantities are crucial for correct motor selection: an undersized motor will not move the load reliably or will overheat; an oversized motor makes the solution more expensive and increases energy consumption. Calculating the required drive torque (T) The drive torque is the torque at the input/worm shaft that is required to move the load (unit: Nm). The following are used for the calculation: Axial load on the screw (F) – in N Screw lead (p ) – travel per revolution (e.g. mm/rev) Overall efficiency of the screw jack (η₍tot₎) – as a decimal value (value from data sheet/tables) No-load torque (T₀) – in Nm (friction torque of the gearbox without external load; tabulated value) Important parameters explained: Overall efficiency (η₍tot₎): depends on the drive type; TR typically lower, KGT very high. Take exact values from the ZIMM data sheets. No-load torque (T₀): torque required to move the gearbox without external load (overcoming internal friction); tabulated value. Note – starting torque: The calculated torque applies to continuous operation. The starting/breakaway torque – especially for TR after standstill – can be higher. The motor must be able to provide this briefly. Calculating the required drive power (P) Drive power indicates how much work the motor has to perform per unit of time. Unit: kW. It depends on the drive torque and the drive speed. The formula for the calculation is: Input values: Required drive torque (T) – in Nm (from the previous calculation) Drive speed (n) – in rpm at the worm shaft (results from the desired lifting speed and the screw lead; take any gear ratio into account if applicable) Power reserve: For a safe design, it is recommended to allow for a reserve of approx. 30% over the calculated power when selecting the motor (among other things for starting torque and mains voltage fluctuations).

Drive torque & power calculation for screw jacks

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Author:

Jonathan Mildner | Head of Sales Technology

Last modified:

21.05.2026

The decisive calculations for selecting the right motor for your screw jack.

Once the gearbox size has been defined on the basis of load capacity, the drive torque and drive power are determined. These quantities are crucial for correct motor selection: an undersized motor will not move the load reliably or will overheat; an oversized motor makes the solution more expensive and increases energy consumption.

Calculating the required drive torque (T)

The drive torque is the torque at the input/worm shaft that is required to move the load (unit: Nm). The following are used for the calculation:

Axial load on the screw (F) – in N
Screw lead (p) – travel per revolution (e.g. mm/rev)
Overall efficiency of the screw jack (η₍tot₎) – as a decimal value (value from data sheet/tables)
No-load torque (T₀) – in Nm (friction torque of the gearbox without external load; tabulated value)

Important parameters explained:

Overall efficiency (η₍tot₎): depends on the drive type; TR typically lower, KGT very high. Take exact values from the ZIMM data sheets.
No-load torque (T₀): torque required to move the gearbox without external load (overcoming internal friction); tabulated value.
Note – starting torque: The calculated torque applies to continuous operation. The starting/breakaway torque – especially for TR after standstill – can be higher. The motor must be able to provide this briefly.

Calculating the required drive power (P)

Drive power indicates how much work the motor has to perform per unit of time. Unit: kW. It depends on the drive torque and the drive speed. The formula for the calculation is:

Input values:
- Required drive torque (T) – in Nm (from the previous calculation)
- Drive speed (n) – in rpm at the worm shaft (results from the desired lifting speed and the screw lead; take any gear ratio into account if applicable)
Power reserve:
- For a safe design, it is recommended to allow for a reserve of approx. 30% over the calculated power when selecting the motor (among other things for starting torque and mains voltage fluctuations).

Jonathan Mildner | Head of Sales Technology

Jonathan Mildner heads the Sales Technology department at ZIMM. He is responsible for the design and safe integration of screw jacks, electromechanical actuators, and drive technology – including accessories from the ZIMM modular system, clearly defined interfaces, the safety concept, and complete documentation; he provides technical support for manufacturing to drawing (special parts/adaptations).

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ZIMM develops and manufactures industrial gearboxes and drive technology for precise linear motion and torque transmission in industrial environments. The portfolio includes screw jacks in 14 sizes with lifting capacities from 2.5 to 1,000 kN, electromechanical actuators from 25 to 200 kN as well as ZK bevel gearboxes in 4 sizes with ratios from 1:1 to 3:1. It is complemented by bevel gearboxes of the KSZ-H, KSZ-2 and KST series, connection technology, motor technology and accessories from the ZIMM modular system, which allows gearboxes, spindles, motors and attachments to be combined into complete lifting systems.

In production according to drawings, ZIMM manufactures drive elements from module 0.3 to 12 and up to Ø 1,500 mm, including spur and bevel gears, worms, as well as ball and trapezoidal screws. Casting, series production and mechanical machining cover turned, milled and cast parts up to a unit weight of 500 kg. Gearbox manufacturing and production according to drawings take place at the headquarters in Lustenau in accordance with ISO 9001:2015; CNC machining at the Sincan/Ankara site is certified according to ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018.