Accurately determining your garage door spring size is critical for safety and operational longevity. Use this professional calculator to find the required IPPT (Inch Pounds Per Turn), door weight capacity, or required turns for your torsion spring system.
Garage Door Spring Size Calculator
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Garage Door Spring Size Calculator Formula
W × R = I × T
Where: W = Weight, R = Drum Radius, I = IPPT, T = Turns
Formula Source: DASMA Technical Standards
Variables:
- Door Weight (lbs): The total weight of the door assembly when balanced.
- Drum Radius (in): The distance from the center of the torsion shaft to the cable groove. (Standard is 2″).
- IPPT: Inch Pounds Per Turn. A measure of the torque a spring generates.
- Turns: The number of full revolutions the spring is wound (typically Door Height in ft + 0.5).
What is a Garage Door Spring Size Calculator?
A garage door spring size calculator is a technical tool used by installers and DIY enthusiasts to ensure the counterbalance system is perfectly matched to the weight of the door. Using an incorrectly sized spring can lead to motor failure or dangerous spring breakage.
This calculator specifically focuses on Torsion Spring mechanics, which rely on the physics of torque. By inputting the door weight and drum dimensions, you can find the exact IPPT required for a replacement spring.
How to Calculate Garage Door Spring Size (Example)
- Measure Door Weight: Use an analog scale under the center of the door (e.g., 160 lbs).
- Identify Drum: Most residential drums are 4″ diameter (2″ radius).
- Determine Turns: For a 7ft door, you usually need 7.5 turns.
- Calculate IPPT: $IPPT = (160 \times 2) / 7.5 = 42.6$.
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Frequently Asked Questions (FAQ)
How many turns should I put on my garage door spring? Generally, one full turn for every foot of door height, plus an extra half turn for tension.
What happens if the IPPT is too high? The door will be “hot” and want to fly open, making it dangerous and difficult for the opener to close.
Can I measure my spring wire diameter with a ruler? It is inaccurate. Use a wire gauge or measure 20 coils and divide by 20 for precision.
Are torsion springs dangerous? Yes. Torsion springs are under extreme tension and can cause severe injury if handled without proper tools and knowledge.