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Machines

Motor Torque Calculator

Estimate steady shaft torque from mechanical power and speed.

01 / Inputs

Shaft power and speed

Enter mechanical shaft power, not electrical input power. The pound-force foot value is the same torque in another unit. This is not a shaft or motor selection.

02 / Result

Shaft torque

Ready to calculate

T = P / ω · ω = 2πn / 60

Torque will appear here.

Method, example and boundaries

For steady rotation, P = T × ω, so T = P / ω and ω = 2πn / 60. Ten kilowatts at 1,800 rpm is 10,000 / (2π × 1,800 / 60) = 10,000 / (60π) = 53.0516… N·m, shown as 53.05 N·m. The same torque is also shown in pound-force feet. Ten kilowatts at 1,500 rpm is 200 / π = 63.6619… N·m, shown as 63.66 N·m.

Enter shaft output power. Do not type electrical input power unless you have already divided it by efficiency outside this page. Zero speed is rejected because this is not a stalled-torque or breakaway model. The result is not a shaft, coupling, keyway, or motor selection.

Source: OpenStax University Physics Volume 1, section 10.8, equation P = τω (SRC-064). The pound-force foot conversion multiplies the international foot 0.3048 m by 4.4482216152605 N; whether NIST SP 811 prints that product in one table cell was not re-checked and is UNVERIFIED. No GB clause changes this relation. The Chinese page shows only the newton metre.

FAQ

What does this calculator compute?

For steady rotation, torque is power divided by angular speed, and angular speed is 2πn / 60. The same torque is shown in newton metres and in pound-force feet.

Which power should I enter?

Enter shaft output power. Do not type electrical input power unless you have already divided it by efficiency outside this page. Zero speed is rejected.

Which conversion is unverified?

Whether NIST SP 811 prints the pound-force foot factor in one table cell was not re-checked and is UNVERIFIED. No GB clause is used to change the relation.

Source records