The easiest way to do this is to take the broken spring to a local garage door dealer or home improvement center so they can help you find an exact match.
How to change extension springs on a garage door.
Replacing garage door extension springs is not a difficult task provided you know all the key steps.
Spotting and removing a bad garage door extension spring.
Spotting a bad garage door extension spring is easy.
How to replace a garage door extension spring.
This video will show you how to replace the extension springs on your garage door.
Granted garage door spring installation work requires time and attention so it is best to save the task for the afternoon of a free day.
Purchase new garage door extension springs.
If the extension springs are not the same length open the garage door and change the location of one of the s hooks so that when you close the door both springs are the same length.
If both springs are the same length the garage door should be level across the floor.
You can see this when your garage door is in the closed position.
If the coils are distended and irregular when the spring is extended then it needs to be replaced.