Torque Power RPM Calculator

Solve shaft power, torque or RPM from the rotating power relation P = T x omega. Works in kW, horsepower, N*m, lbf*ft and rpm. Free, no signup.

Inputs

View results

Solve for

Choose the unknown variable.

Torque (T)

Shaft torque.

N·m

Speed (n)

Shaft speed in revolutions per minute.

rpm

Results

Default result

Edit inputs

Power(P)

15.708kW

Pass

Solved from torque and RPM.

P = T*(2*pi*n/60).

Also computed

Torque(T)100N·m

T = P/omega.

Speed(n)1,500rpm

n = omega*60/(2*pi).

Method notes 2 notes

Uses P = T*omega with omega = 2*pi*n/60. In practical metric form, P(kW) = T(N*m)*n(rpm)/9549.2966.
This is steady shaft power. Add drivetrain efficiency, service factor, startup torque, thermal rating and duty cycle for real motor or gearbox sizing.

Rotating shaft power is P = T*omega, with omega = 2*pi*n/60 from RPM. In metric units, P(kW) = T(N*m)*n(rpm)/9549.2966, and the same equation can be rearranged to solve torque or speed. This calculator works in kW/hp, N*m/lbf*ft and rpm for steady shaft power checks.

How to use this calculator

Choose the unknown. Pick whether you want power, torque or RPM.
Enter the known values. Fill in the two visible inputs for the selected mode.
Check units. Use metric for kW and N*m, or imperial for horsepower and lbf*ft.
Read the solved value. The highlighted output is solved from P = T x omega.
Apply real-world factors. Add efficiency, startup torque and duty-cycle checks when sizing equipment.

How it works

Rotating shaft power is torque times angular speed: P = T x omega RPM converts to angular speed with omega = 2 x pi x n / 60.

With torque in N*m and speed in rpm, the practical metric form is P(kW) = T x n / 9549.2966. Rearranging gives T = P x 9549.2966 / n and n = P x 9549.2966 / T.

For screw drives that convert motor torque into linear thrust, use the lead screw torque calculator so lead, efficiency, thrust and critical speed are included.

Worked example

Verified against the live calculator

A shaft carrying 100 N*m at 1500 rpm has angular speed 157.08 rad/s. Power is 100 x 157.08 = 15,708 W.

That is 15.708 kW, or about 21.06 hp. Solving the other way, 15 kW at 1500 rpm requires 95.49 N*m.

Frequently asked questions

How do you calculate power from torque and RPM?

Use P = T * omega, with omega = 2*pi*n/60. In metric units, P(kW) = T(N*m) * n(rpm) / 9549.2966.

How do you calculate torque from power and RPM?

Rearrange the same relation: T(N*m) = P(kW) * 9549.2966 / n(rpm).

How do you calculate RPM from torque and power?

Rearrange for speed: n(rpm) = P(kW) * 9549.2966 / T(N*m).

Is horsepower supported?

Yes. Toggle to imperial units and the power output displays as horsepower while torque displays as lbf*ft.

Does this include efficiency?

No. It is the shaft power relation at the point you are checking. For motors, belts, gearboxes or hydraulics, apply drivetrain efficiency and service factor separately.

Can zero RPM make torque infinite?

For inverse torque solves, speed must be greater than zero. Static holding torque is not a power calculation because mechanical power is zero when angular velocity is zero.

Method & assumptions

Uses the steady rotating power relation P = T x omega.
RPM is converted with omega = 2 x pi x n / 60.
Power is shaft power at the point being checked; no efficiency is included.
Startup torque, transient loads, thermal limits, service factor and duty cycle must be checked separately for real motors and gearboxes.

Torque Power RPM Calculator

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