Servo Torque Requirement Calculator

Work out servo torque requirement instantly with clear inputs, formula shown and shareable results.

About Servo Torque Requirement Calculator

Servo torque must cover the static gravity moment (mass x g x arm) plus the inertial term (inertia x angular acceleration), then a safety factor. Treating the load as a point mass gives inertia = m r squared, and the arm length appears squared in that term — so a long arm is dominated by acceleration, not gravity.

Formula

Servo torque

T = m g r + m r^2 x alpha, then x safety factor

Worked example

With the default values below, Servo Torque Requirement Calculator returns Torque required of 6.64. Change any input above and every figure here is recalculated in your browser.

Inputs used

Load mass: 1.5 kg
Moment arm: 250 mm
Angular acceleration: 8 rad/s²
Safety factor: 1.5 x

Results

Torque required: 6.64 N·m
Static holding torque: 3.68 N·m
Inertial torque: 0.75 N·m
Torque required: 67.72 kg·cm

Step by step

1Values used
2Servo torque
3Torque required= 6.64 N·m
4Static holding torque= 3.68 N·m
5Inertial torque= 0.75 N·m
6Torque required= 67.72 kg·cm

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why include a safety factor?

Friction, cable drag, unmodelled inertia and voltage sag all reduce real torque. 1.5-2x is normal, more if the motion is fast or the load uncertain.

What about holding torque at rest?

Gravity load must be held continuously, so check the motor's continuous rating, not its peak — peak torque is only available for seconds.