Can you replace just one spring on a garage door?

You can replace just one spring on a garage door if only one is broken, but it is generally recommended to replace both springs at same time when you have two torsion springs, as they have same age and cycles and second spring likely near failure, though replacing one is possible to save cost short term. For garage doors with two torsion springs mounted above door, both springs share load and have same 10,000 cycle lifespan, so when one breaks after 7 to 10 years, the other is also worn and may break soon, often within months, causing second service call costing another 200 to 400 dollars, so replacing both at once costing 300 to 600 dollars total saves labor and avoids being stranded with door stuck. If your door has only one torsion spring, you replace just that one. For extension springs along tracks, you can replace one, but pair replacement recommended for balance. If you replace just one torsion spring, ensure new spring matches old spring in wire size, inside diameter, and length, as mismatched springs cause door unbalanced, opener strain, and uneven wear, and professional will adjust tension to balance. Some homeowners replace one to save money if budget tight, but professional will advise both. If second spring relatively new, such as replaced recently, you can replace just broken one. Warranty may cover pair. In summary, yes you can replace one, but replacing both is better long term for reliability and cost savings.