"Each referral yields 250MB of free space for up to 8GB for Dropbox Basic accounts (for a total of 10GB), and 16GB for Dropbox Pro accounts (in addition to the amount you paid for)! If you're a student, we double the amount for referral bonuses to 500MB per referral up to 16GB for Basic accounts (added to the initial 2GB of free space for a total of 18GB) and up to 32GB of extra space for Pro accounts. "