Servo Sizing Calculator

Size servo motors by checking inertia ratio, RMS torque, and speed requirements for optimal motion control performance.

Load Inertia

kg·cm²

Gear Ratio

Motor Rotor Inertia

kg·cm²

Peak Torque Required

N·m

Motor Continuous Torque

N·m

Duty Cycle

Motor Max RPM

RPM

Required Motor RPM

RPM

Tab to move between fields

Inertia Ratio

1:1

Inertia MatchExcellent

Reflected Load Inertia0.5 kg·cm²

RMS Torque3.54 N·m

Est. Bandwidth100 Hz

How to Use This Calculator

Enter load inertia (kg·m²) reflected at the motor shaft and the gear ratio.
Set motor rotor inertia (kg·m²) from the motor manufacturer's specification.
Enter peak torque required (N·m) and motor continuous torque rating and duty cycle (%).
Review inertia ratio — values above 10:1 indicate potential stability issues; target below 5:1.
Check RMS torque and bandwidth (Hz) to confirm the servo meets dynamic response requirements.

How the result changes with Gear Ratio

Load Inertia: Total load inertia at the gearbox output shaft.
Gear Ratio: Gearbox reduction ratio (e.g., 10:1).
Motor Rotor Inertia: Motor rotor inertia from the motor datasheet.
Peak Torque Required: Maximum torque needed during acceleration/deceleration.
Motor Continuous Torque: Motor continuous torque rating from datasheet.
Duty Cycle: Percentage of time the motor is under peak load.
Motor Max RPM: Maximum rated speed of the servo motor.
Required Motor RPM: Required motor shaft speed for the application.

Identify Input Parameters
4 parameters
Load Inertia = 50, Gear Ratio = 10, Motor Rotor Inertia = 0.5, Peak Torque Required = 5 = 8 input(s) provided
Calculate Inertia Ratio
Inertia Ratio
1 = 1
Calculate Inertia Match
Inertia Match
Excellent = Excellent
Calculate Reflected Load Inertia
Reflected Load Inertia
0.5 = 0.5