The best way to work out how much RAM your model can take is to go to the Crucial website and select your model.

You can often max it out beyond what Apple advertise and offer. For example the MacBooks from the last few years can be maxed out to 16GB, even though Apple claim they max out at 8GB and never offer 16GB as an option at purchase.

(Apple aren't the only company who do this, I've also owned one NEC and three Dell machines that were upgradable beyond what the manufacturer said, in all cases I bought the RAM from Crucial on the basis that they said it could support the higher amount so it was down to them if it didn't work properly)