Motor Torque, Power and Speed Calculator
Solve rotational power, torque or speed from the other two quantities with explicit torque and speed units.
YOUR CALCULATION
Result
—
Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert torque to newton-metres and rotational speed to radians per second. Apply the instantaneous shaft-power identity, rearranging it only when torque or speed is the requested unknown.
P=τω; τ=P/ω; ω=P/τ
Worked example
A 12 N·m shaft at 1,200 rpm transmits about 1.508 kW. At 1.5 kW and 1,200 rpm, the corresponding torque is about 11.94 N·m.
Assumptions and input details
Values are non-negative magnitudes for steady rotation. Power is mechanical shaft power at the same point as the torque and speed; do not mix electrical input power with output torque unless efficiency is handled separately. Calculating torque requires nonzero speed and calculating speed requires nonzero torque. Startup, transient, overload, gearing, losses, thermal limits and motor ratings are excluded.
References: OpenStax: power in rotational motion
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
SI prefixes are explicit: for example, milli means one thousandth, micro one millionth and kilo one thousand. Changing a unit changes the interpretation of the entered number.
One revolution is 2π radians or 360 degrees. One minute is 60 seconds, so 1 rpm = 2π/60 rad/s. Rotational frequency in hertz counts revolutions per second.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
Convert rpm, angular speed and tangential rim speed using a radius or diameter. Find frequency, period and centripetal acceleration with explicit units.
Calculate work done by a constant force over a displacement. Account for the angle between force and motion, including zero and negative work.
Compare input energy with useful output over the same time. Find average input/output power, energy loss and conversion efficiency.
Reserved advertising space.