Roller Blind Motor Torque Guide: How Many Nm Do You Need?
Updated: Aug 31
Choosing specifically between Somfy motors? Start with the Somfy Roller Blind Motor Buying Guide Australia.
Roller blind motor torque is measured in Newton metres, written as Nm. It describes the turning force available to rotate the tube and lift the blind. The correct torque is not chosen from width alone: fabric weight, drop, tube diameter, hardware friction and whether blinds are linked all matter.
Before comparing Nm ratings, confirm the motor can physically fit the tube. Our roller blind motor range groups current Automate and Somfy options, while the tube identifier handles retrofit compatibility.
What Nm means on a blind motor
A higher Nm figure means more turning force. It does not automatically mean the motor is quieter, faster, smarter or better quality. Those are separate specifications.
The motor must provide enough torque to lift the blind reliably with a sensible operating margin. Too little torque can cause stalling, inconsistent movement and unnecessary strain. More torque than needed can add cost and size without solving tube or installation problems.
The five factors that determine torque
1. Fabric weight
Blockout, sunscreen and light-filtering fabrics can have different weights. A wider and longer piece of fabric creates a greater load. Bottom rails and decorative hardware also add weight.
2. Blind width and drop
Width increases the amount of fabric and can increase tube deflection. Drop affects how much fabric is hanging and how much material is rolled onto the tube. Two blinds with the same width can require different motors if their drops or fabrics differ.
3. Roller tube diameter
Tube diameter changes the mechanical leverage at the motor. As fabric builds up on the roller, the effective roll diameter increases and the motor may need more torque. The tube also has to be stiff enough for the blind width.
4. Hardware and installation
Bracket alignment, idler condition, tube straightness and fabric tracking all affect resistance. A motor should not be oversized to hide a bent tube or binding hardware; the mechanical issue should be corrected.
5. One blind or linked blinds
A motor driving two linked blinds carries more load than a motor driving one. Linked systems also add couplers and alignment requirements. This is where higher-torque motors, including 6Nm options, can become useful.
Practical residential torque bands
These bands are a guide, not a substitute for a load calculation or the motor manufacturer's limits.
Around 0.7Nm: very small, light roller blinds where the motor and tube are specifically compatible.
Around 1.1–1.5Nm: many ordinary residential roller blinds with a suitable tube and fabric load.
Around 2Nm: larger or heavier residential blinds where the calculated load exceeds the smaller motors.
Around 4–6Nm and above: large, heavy, linked or specialist blinds that have been designed for the additional load.
The Automate range currently includes Q rechargeable motors at 0.7Nm, 1.1Nm and 2.0Nm, plus a 6Nm rechargeable motor for applications that genuinely need the extra torque.
Why width-only rules can be misleading
A statement such as “this motor suits a two-metre blind” is incomplete unless the fabric, drop, tube and installation are also known. A light sunscreen blind and a heavy blockout blind at the same width are not the same load.
Tube stiffness also matters. A stronger motor cannot stop an undersized tube from bowing. On wide blinds, the correct answer may be a stronger tube and a different motor format rather than simply increasing Nm.
What happens if the motor is undersized?
The blind may stop or struggle on the way up.
Movement can become inconsistent as the battery charge falls.
Limits may appear unreliable because the motor cannot complete the travel.
Repeated stalling can shorten component life.
Can a motor be too powerful?
Yes, in the sense that the motor may be unnecessarily large, expensive or incompatible with the tube. The correct motor is the smallest suitable model that meets the calculated load, tube and duty requirements with an appropriate margin.
More torque does not compensate for the wrong crown and drive, unsuitable brackets, a weak tube or a blind that is mechanically binding.
How to choose the right torque
Record the finished blind width and fabric drop.
Identify the fabric type or obtain its weight per square metre.
Confirm the tube profile, outside diameter and structural suitability.
Include the bottom rail and any linked-blind hardware in the load.
Use the relevant motor load chart or ask us to confirm the motor before ordering.
Torque is only one part of the decision
After torque, choose the power type using our rechargeable vs 240V vs 12V guide, then compare Automate and Somfy for the controls and ecosystem you want.
What information should you send us?
Send the blind width, drop, fabric type, tube profile or a clear tube-end photo, and whether it is a single or linked blind. If the blind already exists, also include photos of both brackets. That is enough for us to narrow the motor and adaptor options accurately.
For the full selection process, read What Motor Do I Need for Roller Blinds?.
