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Motor Performance Toolkit

Motor Torque, Speed & Power Calculator

Use Alto's motor torque calculator to solve for torque, RPM or mechanical power and instantly estimate motor input watts and amps across DC, single-phase AC or three-phase AC supplies.

This motor power and current calculator supports BLDC, PMSM and AC induction motors, guiding you through the efficiency and power-factor inputs you need to size controllers, batteries and cabling with confidence.

Mechanical Power Calculator

Choose which value to solve for and provide the other two inputs. Mechanical power follows Power_mech (W) = Torque (Nm) * 2 * π * Speed (RPM) / 60. This represents the shaft output power shown on a motor name plate, so the rated power listed by the manufacturer usually reflects this mechanical wattage.

Solve for:

Electrical Input Calculator

Estimate the electrical requirements for your motor by first selecting the power supply type that matches your setup. Use DC power for DC motors such as BLDC or PMSM, Single-phase AC for single-phase induction motors, and Three-phase AC for three-phase induction motors. Enter the line voltage (line-to-line for three-phase) and include the manufacturer-specified power factor for AC motors, typically between 0.80 and 0.95, to ensure the current estimate accounts for real-world efficiency losses. The mechanical wattage can be taken directly from the torque calculator above or entered manually, while the efficiency factor should be provided by the motor manufacturer. For those interested in the underlying calculations, the guide below outlines the formulas used for each parameter.

Supply type:

How the calculations work

Mechanical Power

Mechanical power is derived from torque and rotational speed using Power_mech (W) = Torque (Nm) * 2 * π * Speed (RPM) / 60. This is the shaft output power shown on the motor name plate, so the rated power published by the manufacturer almost always refers to this mechanical wattage.

Electrical Input

Electrical input power accounts for conversion losses. Gather the efficiency value and, for AC, the power factor from your motor manufacturer - these figures are rarely printed on the name plate. DC current follows Current (A) = Power_in (W) / Voltage (V). Single-phase AC current uses Current (A) = Power_in (W) / (Voltage (V) * Power factor). Three-phase AC line current relies on Current (A) = Power_in (W) / (√3 * Voltage (V) * Power factor). Because of those losses, electrical input power is always higher than the rated mechanical power when you size controllers, inverters or batteries.

Motor calculator tips

Use this page as your all-in-one motor power and torque calculator for sizing BLDC, PMSM, Servo, or AC induction motors. Start with torque and RPM to determine the required mechanical power, or enter your rated wattage to back-calculate torque or speed needs. Switch to the electrical section to verify voltage, current draw and power factor before selecting suitable motor controllers or power supplies.

This tool helps engineers, OEMs and hobbyists make precise calculations for torque, speed, power and current draw across a wide range of applications - from e-mobility and robotics to process automation. Keep manufacturer data such as efficiency curves and expected power factors handy so your current estimates stay realistic and your team can communicate motor requirements with confidence.