15mm vs 25mm vs 45mm Tubular Motor Sizes: What They Mean and How to Choose the Right One

Tubular motors continue to be the backbone of modern motorized blinds, roller shutters, and automated shading systems. Yet for many engineers, OEMs, integrators, and procurement teams, the question remains deceptively simple: What is the real difference between 15mm, 25mm, and 45mm tubular motors—and which one should you specify?

Although the numbers look straightforward, each motor diameter reflects a very different performance class, torque capability, and application window. The choice affects not only lift capacity and reliability but also compatibility with tube diameter, installation constraints, noise profile, and long-term serviceability.

This guide breaks down the practical distinctions between these three core motor classes and provides a grounded, engineering-friendly perspective on how to match motor size to shade design, load, and project requirements.

Understanding What “15mm /25mm / 45mm” Really Means

A tubular motor's size classification refers to the motor's outer diameter. Because the motor sits inside an aluminum shade tube, the tube's internal diameter must exceed the motor diameter and also match the manufacturer's drive adapters and crown wheels. To dive deeper into the internal structure, stator–rotor interaction, and how torque is generated in these systems, you can refer to our overview on how tubular motors are engineered and how they work.

In practice, the motor size determines more than just fit. It directly influences torque, power, heat management, and the type of window or opening the motor can operate.

A smaller motor means lighter duty. A larger motor means higher torque. But the nuances between 15mm, 25mm, and 45mm motors make selection more strategic than it appears at first glance.

15mm Tubular Motors: Compact Size for Light-Duty Window Shades

The 15mm motor is the smallest and most compact form factor commonly used in residential light-duty shades. These motors are typically paired with small- to medium-sized roller tubes—often around 38mm outer diameter—and are engineered for minimal load scenarios where space efficiency is a priority.

1. Where 15mm Motors Excel

In small window openings, lightweight blinds, and modern minimalist interiors, a motor with minimal footprint has clear advantages. These motors provide sufficient torque to lift standard fabrics and basic roller shades without stressing the drive system. They are particularly attractive in apartments, small rooms, and applications where aesthetics require slim tubes.

2. Load and Performance Expectations

Because of their smaller diameter, 15mm motors inherently produce lower torque. This does not restrict their usefulness; instead, it positions them precisely where they belong—operating light loads efficiently and quietly. They are well-suited for zebra blinds, small sunscreen fabrics, and shorter drops where fabric weight is modest.

3. Best Fit Applications

When the project involves narrow window frames, budget-sensitive light blinds, or installations where larger motors would either not fit or not provide additional value, the 15mm class is often the correct choice. They deliver the essential performance without unnecessary power overhead.

25mm Tubular Motors: The All-Purpose Standard for Most Residential Shades

If there is a“workhorse” size in tubular motor design, it is the 25mm motor. This diameter is widely compatible with standard residential roller tubes, often in the 1.5-inch (≈38mm) class, making it the de facto choice for mid-size shades.

1. Why25mm Has Become the Default

The 25mm motor strikes a balance between compact packaging and meaningful torque output. For most average-size shades in living rooms, bedrooms, and offices, this motor provides enough lifting power without jumping to the larger 45mm class.

It is also an installer-friendly option because its accessories, adapters, and tube pairings are among the most commonly available in the market. This reduces lead times, simplifies procurement, and makes field replacement straightforward.

2. Performance Characteristics

Compared with a 15mm motor, the 25mm unit offers noticeably higher torque margins. This makes it more suitable for mid-weight fabrics, wider shades, or blackout materials that weigh more per square meter. It also tends to maintain better thermal stability, as the larger diameter provides slightly more room for heat dissipation.

3. Ideal Use Scenarios

When a project specifies standard residential roller shades, medium-width windows, or any configuration that is too heavy for a15mm motor but does not require industrial-grade capability, the25mm size is usually the optimal match. It hits a performance sweet spot without inflating cost, footprint, or installation complexity.

45mm Tubular Motors: Heavy-Duty Power for Large Shades and Heavy Fabrics

Moving into the 45mm class brings the motor into a different category entirely. These motors are engineered for large, wide, or high-drop shades where fabric weight, tube inertia, and starting torque requirements exceed the capacity of the smaller sizes.

1. Heavy-Duty Capability

The larger diameter allows for significantly higher torque output. This is crucial for long spans, wide-opening windows, commercial facades, and blackout fabrics with substantial mass.

2. Stability and Thermal Management

Beyond torque, the larger motor body enables better heat dissipation and more robust gearing. This stabilizes performance under continuous or frequent cycling—an important consideration for commercial buildings, public facilities, and automated lighting-control environments.

3. Where 45mm Motors Become Necessary

Whenever shade weight increases, tube wall thickness grows, or a larger roller tube (50mm, 60mm, or even 70mm+, JIECANG can achieve 60mm) is specified, the 45mm motor becomes the natural partner. Engineers often select it not because smaller motors cannot fit, but because smaller motors cannot reliably handle the mechanical load over time.

How to Choose: Matching Tube Size, Torque, and Load

Selecting between 15mm, 25mm, and 45mm motors is not simply a matter of physical fit. The correct specification depends on three intertwined variables: shade weight, shade size, and tube structure.

1. Shade Weight: The Most Critical Variable

Load dictates torque. Light fabrics and short drops place little demand on the motor, allowing smaller sizes to operate comfortably. As fabric thickness, width, or drop length increases, load scales up quickly. A 15mm motor that works perfectly for a small transom window may fail or overheat when asked to lift a wider blackout shade.

2. Shade Size and Tube Diameter

The tube diameter determines the motor class that can physically be inserted. A thicker or larger-diameter tube is not only stronger, but it also changes the lifting geometry, requiring more torque to start rotation. Larger shades often use bigger tubes to avoid deflection, and those tubes naturally accommodate 45mm motors more readily.

3. Compatibility and Mechanical Interface

Adapter rings, drive splines, and crown wheels must match both motor and tube. This is an area where installers sometimes run into avoidable problems. A motor may fit physically but fail to engage the tube correctly if the accessory interface is mismatched. That can lead to slippage, noise, or premature wear.

Practical Selection Guidance Based on Real-World Scenarios

1. When a 15mm Motor Is the Right Choice

If the shade is small, lightweight, or mounted in a tight space, the15mm motor provides all the functionality needed. Its slim form factor simplifies integration in narrow casings or design-forward applications.

2. When to Move Up to 25mm

For standard living-room, bedroom, or office roller shades, the25mm motor is the most versatile and reliable option. It offers enough torque margin to avoid strain and suits the majority of tube systems used in mainstream roller shade manufacturing.

3. When Only a 45mm Motor Will Deliver Performance

Large sliding doors, commercial environments, heavy blackout fabrics, acoustic shades, exterior roller shutters, and long-span architectural shading systems typically require a 45mm motor. In these conditions, torque, thermal stability, and long-term durability are non-negotiable.

Comparison Table: 15mm vs 25mm vs 45mm Tubular Motors

Conclusion

Choosing between a 15mm, 25mm, or 45mm tubular motor is ultimately about aligning motor capability with shade size, fabric weight, and long-term performance expectations. Smaller motors are excellent for compact, lightweight blinds, while mid-size motors offer the versatility required for most residential applications. Heavy-duty motors, meanwhile, provide the power and durability needed for large spans and demanding environments.

Finally

JIECANG has been deeply engaged in the research and development of Tubular Motors in the smart home field.If you need help specifying the right tubular motor for your smart home project, JIECANG can assist with technical comparisons, torque calculations, and motor-selection guidance.