Example Data Table
| Example |
Width |
Height |
Fabric |
Tube |
Bottom bar |
Estimated minimum torque |
| Small kitchen blind |
2.5 ft |
1 ft |
260 g/m² |
1 in |
0.16 lb/ft |
0.11779 N·m |
| Office blind |
4 ft |
1 ft |
350 g/m² |
1.25 in |
0.22 lb/ft |
0.29216 N·m |
| Heavy blackout blind |
5 ft |
1 ft |
520 g/m² |
1.5 in |
0.3 lb/ft |
0.58585 N·m |
Formula Used
Area: Area = width × height.
Fabric mass: mass = fabric GSM ÷ 1000 × area in m².
Tube turns: turns = blind height ÷ tube circumference.
Static torque: torque = hanging weight × gravity conversion × average roll radius.
Friction torque: friction torque = static torque × friction percentage.
Acceleration torque: acceleration torque = moving mass × radius² × angular acceleration.
Motor torque: required torque = total torque ÷ mechanical efficiency × safety factor.
Speed: required rpm = tube turns ÷ travel time × 60.
Power: shaft power = torque × angular speed.
Current: current = electrical power ÷ voltage.
How to Use This Calculator
Enter the blind width and keep the height at one foot unless your design is different.
Add fabric weight, fabric thickness, tube diameter, tube weight, and bottom bar weight.
Use a higher friction value for tight brackets, side channels, or rough bearings.
Choose a safety factor. Use more margin for outdoor, dusty, or frequent operation.
Enter voltage, efficiencies, desired travel time, and estimated motor speed.
Press Calculate. The result appears above the form and below the header.
Download the CSV or PDF report for project records and motor comparison.
Advanced motor selection for a one foot blind
A one foot tall roller blind looks small. Yet its motor still needs careful sizing. Width, fabric density, tube diameter, friction, and speed all change the result. A short drop may use few tube revolutions. The starting torque can still be high when brackets drag or the hem bar is heavy.
Why torque matters
Torque is the turning force at the roller tube. The calculator converts the hanging blind weight into tube torque. It then adds friction, acceleration torque, efficiency loss, and a safety factor. This gives a practical minimum motor torque. A motor below this value may stall, hum, heat, or miss limit positions.
Why speed matters
Speed decides how quickly the blind moves. A small blind can finish travel with less than one full tube turn. Very high speed may look rough. Very low speed may feel sluggish. The tool estimates tube revolutions, required rpm, shaft power, and approximate current. These values help compare direct drive, geared motors, and tubular shade motors.
Electrical checks
Voltage and efficiency affect current. A low voltage motor draws more current for the same mechanical power. Cable length, controller rating, relay contacts, and battery capacity should match the estimated current. Always choose a driver with extra margin. Soft start control can reduce shock loads and noise.
Mechanical checks
Small blinds often fail because of alignment, not calculation. Keep brackets square. Let the tube rotate freely. Avoid fabric rubbing inside side channels. Use a balanced bottom bar. Check that the selected motor fits the tube bore and mount type.
Selection advice
Use the result as a design guide. Pick the next larger standard motor size. Confirm stall torque, rated torque, rated rpm, duty cycle, thermal limits, and limit switch style from the motor data sheet. For outdoor, damp, or high use locations, add more safety margin. Test one prototype before ordering many units.
Practical limits
When the blind is only one foot tall, measurement errors become more important. A small radius change can shift torque and rpm. Enter realistic fabric thickness and tube size. Do not use stall torque as normal working torque. Rated torque should carry the blind repeatedly without overheating during daily cycling safely.
FAQs
1. What motor torque should I choose?
Choose a motor with rated torque above the calculator result. Do not rely on stall torque. Rated torque is the safer value for repeated operation.
2. Why is safety factor important?
It covers friction, fabric swelling, imperfect brackets, voltage drop, and aging. Small blinds still need margin because real hardware rarely acts ideally.
3. Can I use this for taller blinds?
Yes. Change the height input. The tool will update tube turns, speed, radius estimate, torque, power, and current for the new drop.
4. Does tube diameter affect motor size?
Yes. A larger tube radius increases torque. It can reduce turns, but the motor must still overcome the larger lever arm.
5. What voltage should I enter?
Use the actual motor supply voltage. Common values include 5 V, 12 V, 24 V, and mains powered systems with suitable controllers.
6. Why include fabric thickness?
Fabric thickness changes the roll radius as fabric wraps around the tube. This affects torque and speed, especially with thicker blackout material.
7. Should I select the exact calculated torque?
No. Select the next larger available motor size. Also check physical fit, duty rating, limit switches, noise, and controller capacity.
8. What causes a small blind motor to stall?
Common causes include weak torque, tight brackets, tube rubbing, poor alignment, low voltage, overloaded bottom bars, and undersized motor drivers.