How Many Cans Freon To Put In Empty Car Ac?

If it's empty due to a leak, you need to fix the leak or no amount will be correct.
If it is due to a component part replacement then one 12 oz can will get the system running, but don't forget the 2 oz of oil.
You will need to evacuate the system after the repair or replacement. This is a process of removing the air and moisture from the inside of the a/c system. If you don't have a vacuum pump and a set of gauges, take it to a shop for the process and have them charge it. They will weigh the proper amount of refrigerant in.

You need to look on the underhood sticker, it will say how much freon to use.

Most average sized vehicles take about 2 cans, big Ford & Dodge trucks take almost 3 to fill from scratch. Good luck:)