what size garage door extension springs do i need

1. The size of the garage door
The height of the door: directly affects the length and number of turns of the spring (e.g. 2.4 meters, 3 meters, etc.).
Door weight: The strength of the spring needs to match the weight of the door (usually expressed in pounds or kilograms). Common Home Garage Door Weight Range:
Single-layer steel plate door: 40-80 kg
Double insulated doors: 80-120 kg
Wooden doors: may be heavier.

2. Types of springs
Left-Wound and Right-Wound: Depends on the mounting position (usually a pair of springs will be installed symmetrically on the left and right).
Spring Inner Diameter (ID): Common sizes such as 1.75" (44 mm), 2 inches (51 mm), etc., need to be matched with the spring shaft.
3. Specifications of the spring
Wire Size: The thicker the wire, the higher the load-bearing capacity (e.g. 0.243 inches, 0.262 inches).
Spring length: usually related to the height of the door (e.g. a 2.4 m door height may require a 0.6 m long spring).
Number of laps: determined by door weight and height (e.g. 20 laps, 30 laps).

4. Other Necessary Information
Opening Method: Standard vertical lift, high lift or low headroom designs will affect the spring strength requirements.
Existing spring markings: If replacing an old spring, check the label or engraving on the spring (e.g., "225-2-24" means: 225 lb. weight, 2 inches ID, 24 turns).
5. Professional advice
Calculation tool: Use the online spring calculator (enter the door weight, height, etc. for automatic recommended specifications).
Consult the supplier: After providing the above information, the supplier can help you match the model
Safety Tips: Torsion spring installation is dangerous and recommended to be carried out by professionals.

Example calculations
Assume a double-walled steel door (2.7 meters high and 90 kg in weight):
A pair of 0.262-inch wire diameter, 2-inch I.D., 34-turn springs may be required, depending on the design of the door opening system.
Make sure all parameters are accurate, otherwise it may lead to premature spring failure or unbalanced door body!