It doest matter how big of an air compressor do you need to blow out my sprinklers? If the compressor providing you requires pressure to blow out sprinklers that is enough.
If you are going to buy a compressor for that, you must find a compressor that is capable of providing
20 to 25 cubic feet per minute (CFM) of air volume. Most of the professionals also recommend at least 50 CFM to better pull our water from the pipeline.
And the storage capacity of that compressor is 4-6 gallons, which means you do not need to go with a big one whose capacity is more around 15-above gallon, or that also means to go with a small size 1-3 gallon.
The Best Air Compressor For Blowing Out Sprinklers (Blowing Out Water Lines)