Dropbox Basic accounts start with 2 GB of free space. You can earn more free space in a variety of ways. For example, by referring your friends to Dropbox, you can earn up to 16 GB of additional space.
If you ever run out of space, you can upgrade your account with a monthly or yearly subscription to a Dropbox Pro 100 GB, 200 GB, or 500 GB plan. If you're an organization or group looking to share an even larger amount of space together, you may be interested in Dropbox for Business.