Torque to Power Calculator: P = torque x angular speed

The power of a rotating shaft from its torque and speed.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose which quantity you want to find.

Enter the other values in the units shown.

The calculator gives the answer with the formula, the substituted numbers, and the answer in other units.

Formulas used

  • P = \tau\,\omega
  • \tau = \frac{P}{\omega}
  • \omega = \frac{P}{\tau}

Worked example

With the default numbers in the calculator above:

  1. The formula, arranged to find the power: power = torque x angular speed
  2. Put the values in (every value in its SI unit): power = 50 x 157.08
  3. The answer: power: 7853.98 W
  4. The same answer in other units: 7.85398 kW; 10.5324 horsepower

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

How do I find the power from torque and rpm?

Power in watts equals torque in newton metres times the speed in radians per second. 50 N m at 1500 rev/min is 7854 W.

How do I convert rev/min to rad/s?

Multiply by 0.10472 (2 pi over 60).

How do I find the torque of a motor?

Divide the power by the angular speed.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any school physics or engineering text (rotational power).

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