You may need to use a 2x4 or some other object to pry the garage door open.
Garage door extension spring proper installation.
This video will show you how to replace the extension springs on your garage door.
Torsion see above which mounts on the header above the door and extension photo 1 which floats above the upper roller track.
Installation of a standard extension spring for an ideal garage door.
Do not use a digital scale as they often will not respond to the door weight changing as rollers no longer stick to the track.
A few years back i narrowly avoided being hit by a spring that snapped.
Purchase new garage door extension springs.
Tie the extension spring to the roller track then detach the cable from the bottom bracket with a pair of pliers.
Garage door springs come in two styles.
Place scale under the garage door on the side of the door with the broken extension spring.
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.