BIZOMAT MAKEOS · Power Transmission
Torque, Power and Speed
What shaft torque corresponds to this power and speed?
Convert mechanical shaft power and rotational speed into steady torque.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Mechanical shaft power | kW | Delivered mechanical power at this shaft, not motor electrical input. |
| Shaft speed | rpm | Operating speed at the same shaft where power is specified. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Mechanical shaft power
- What it is
- The mechanical power delivered at this shaft, the useful output rather than the electrical power drawn by the motor.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0 kW to 1000000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Torque is directly proportional to power at a fixed speed.
- Get it right
- A motor’s nameplate kW is its rated shaft output; electrical input is higher because of losses.
What this means: Shaft speed
- What it is
- The rotational speed of the same shaft at which the power is delivered.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.001 rpm to 1000000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1500 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Torque is inversely proportional to speed for the same power.
- Get it right
- After a gearbox, use the output shaft speed with the output power, not the motor speed.
Method and formulas
- Angular speed = 2 × π × RPM / 60.
- Torque (N·m) = power (kW) × 1000 ÷ angular speed.
- Example: 5 kW at 1500 rpm corresponds to 31.830989 N·m.
Limitations
- Steady mechanical power only; no start-up, shock, stall or duty-cycle rating.
- Efficiencies must be applied before entering output shaft power.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- motor torque
- shaft power
- rotational speed
Who it is for
- Designers
- Maintenance teams
What you get
- Shaft torque
- Angular speed
- Mechanical power
Interpreting the result
- Use the actual torque-speed envelope for drive selection.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 176, 186, 295–297, 2573. Topic reference; no source tables or recommended settings are reproduced.
- Parker: Basic Hydraulic Formulas — https://www.parker.com/content/dam/Parker-com/Literature/Accumulator---Cooler-Division---Americas/Catalogs---Bulletins/GAD-HY10-1630-5-2012/ACD_CoolerCatalog_HY10_1700.pdf
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Magnetic couplings and sealless pumps
In Permanent Magnets in Machines by the Numbers
What it covers: Size a magnetic coupling for a sealless pump: shaft power, running and starting torque, temperature derating, eddy losses in the containment shell, and what dead-heading or dry running does.
Useful alongside · BIZOMAT original book
Torque to speed up and slow down
In Inertia and Flywheels by the Numbers
What it covers: How much torque it takes to bring a rotor to speed or stop it in a given time, how many turns and how much energy that involves, and how a motor's rating compares with the torque the change needs.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.