17 — Calculators
Torque from power and speed
The shortest useful formula in drive engineering: torque follows from power and speed. You need it for every gearbox selection and every check whether a motor will start the machine at all.
Result
- Torque
- —Nm
- Angular velocity
- —rad/s
Please fill all fields with valid numbers.
- Opens the print dialog. Choose “Save as PDF” as the destination.
- Opens your email program with the values from this calculation. Nothing is sent to us until you send it yourself.
A guide, not a design to standard. We give no warranty for the correctness of the results, the applicable standards and case-by-case verification govern.
Worked example
The default case the calculator starts with, worked through once. Change the values above and it recalculates immediately.
Inputs
- Shaft power
- 7.5 kW
- Speed
- 1,450 min⁻¹
Result
- Torque
- 49.4 Nm
- Angular velocity
- 152 rad/s
Formula
- M = 9550 · P / n (P in kW, n in min⁻¹, M in Nm)
- ω = 2π · n / 60
Assumptions and standards
- The constant 9550 comes from 60,000 / 2π and applies to power in kilowatts and speed in revolutions per minute.
- The result is rated torque at the operating point. Starting, pull-up and breakdown torque differ considerably and are given in the motor data sheet.
Frequently asked
Does the formula apply to geared motors?
Yes, if you enter the output speed. Output torque rises with the gear ratio, less the gearbox efficiency.
Why is rated torque not enough for sizing?
Because the critical point is usually starting. A machine with high breakaway torque needs a multiple of rated torque, starting torque governs there, not the value calculated here.
Calculating is the easy part.
A formula gives you a number. Designing a plant also demands installation method, grouping, discrimination, the standards in force and a look at the installed base. That is what we take on.
More tools
- 01Cable cross-section
- 02Voltage drop
- 03Cable resistance
- 04Cable losses
- 05Maximum cable length
- 06Current-carrying capacity
- 07Parallel cables
- 08Conductor temperature
- 09Cable capacitance
- 10Short-circuit current
- 11Cable impedance
- 12Network impedance
- 13Short-circuit current at the far end
- 14Thermal short-circuit withstand
- 15Length and disconnection
- 16Motor current
- 18Starting current
- 19Star-delta starting
- 20Soft starting
- 21Motor efficiency
- 22Speed control instead of throttling
- 23Speed and slip
- 24Setting the motor protection
- 25Single-phase motor
- 26Motor feeder
- 27Required motor rating
- 28PFD and SIL
- 29PFH and SIL
- 30Protective conductor size
- 31Earth rod
- 32Touch voltage
- 33Residual current protection
- 34Check discrimination
- 35Connecting a surge arrester
- 36Enclosure cooling
- 37Reference designation
- 38Reactive power compensation
Contact
Tell us what it is about.
A phone call or three lines is enough. From the very start you talk to the people who will later work on your project, not to a distribution list.
Direct
- Phone+49 (0) 5247 4070-66
- Emailinfo@fisekon.com
- AvailabilityMon – Fri, 8:00 – 17:00 CET
Locations
33428 Marienfeld (Harsewinkel)Gütersloh officeWagenfeldstr. 2
33332 Gütersloh
Or write to us
We usually reply within one working day.