What is torque in the context of a servo motor?

Torque is the rotational force a servo can exert. It equals the load force multiplied by the distance from the pivot (moment arm). A heavier load or longer arm requires more torque.

Why use a safety factor?

Servo torque ratings are measured at stall under ideal conditions. Real-world friction, inertia, and acceleration peaks can exceed the static load calculation. A safety factor of 1.5–2.0 provides headroom so the servo does not overheat or strip its gears.

How do I convert between oz-in, kg-cm, and N-m?

1 kg-cm = 0.980665 N-m / 100 = 0.00980665 N-m. 1 oz-in = 0.00706155 N-m. This calculator handles all conversions automatically once you enter the inputs.

What is the moment arm?

The moment arm (lever arm) is the perpendicular distance from the servo shaft center to the line of action of the load force. For a straight horizontal arm it is simply the arm length.

Does this account for the weight of the arm itself?

No — this calculator focuses on the tip load. To account for arm weight, add half the arm mass as an additional load at the midpoint, then sum the torques.

Which unit should I use to select a servo?

Hobby servos are commonly rated in kg-cm or oz-in. Industrial and brushless servos use N-m. Match the unit to your datasheet to avoid conversion errors.

Servo Torque Calculator

Name: Servo Torque Calculator
Availability: InStock
Author: Nham Vu

Enter load weight, arm length, and safety factor to find the minimum servo torque in oz-in, kg-cm, and N-m.

Inputs

Load Weight

Mass of the object the servo must move (at the tip of the arm).

Arm Length (Moment Arm)

Distance from the servo shaft center to the load attachment point.

Safety Factor

Multiplier applied to required torque. Recommended: 1.5 – 2.0.

Enter values and click Calculate to see torque results.

Summary

Enter load weight, arm length, and safety factor to find the minimum servo torque in oz-in, kg-cm, and N-m.

How it works

Enter the load weight (mass at the tip of the arm) in your preferred unit.
Enter the arm length (distance from the servo shaft to the point where the load acts).
Set the safety factor — 1.5 to 2.0 is recommended for most applications.
The calculator computes torque = load force × arm length × safety factor.
Results appear instantly in oz-in, kg-cm, and N-m so you can match any servo datasheet.
Use the result to select a servo whose rated stall torque exceeds the required value.

Use cases

Sizing servo motors for robotic arm joints.
Selecting pan-and-tilt servo for camera gimbals.
Designing RC airplane control surfaces and linkages.
Calculating torque for gripper and claw mechanisms.
Verifying existing servo selection before a build.
Educational projects and STEM coursework involving servo mechanics.
Comparing servo specs from datasheets using common unit conversions.
Estimating torque margins for multi-axis manipulators.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu