Can you use a MacBook Air charger for a MacBook Pro? The short answer: You shouldn’t.
Why not? The MacBook Air has a 45W adapter and the MacBook Pro has a 85W adapter. You definitely can use a MacBook Air charger for a MacBook Pro but it’s not good for the battery or the MacBook.
Here’s what Apple has to say:
Power adapters for Mac notebooks are available in 29W, 45W, 60W, 61W, 85W, and 87W varieties. You should use the appropriate wattage power adapter for your Mac notebook. You can use a compatible higher wattage adapter without issue, but it won’t make your computer charge faster or operate differently. Lower wattage adapters don’t provide enough power.
What can it do to your MacBook Pro if you do decide to use a MacBook Air charger to charge it? The MacBook Pro charger may manage to power your MacBook Pro but it won’t charge it. You might also notice that the battery might deplete when you’re using your MacBook.