In the UK degrees are graded as 1st class, upper second class (2:1), lower second class (2:2), third class (these are the honours classifications), pass and fail. Usually this is 70%, 60%, 50%, 40%, 30% (or 40% in fewer modules) and anything less. However these percentages don't translate to the US or Australian system as is - by general guidelines a first is usually considered the equivalent of about a 3.7 GPA on the US system. For those universities that do it, magna cum laude is roughly equivalent to a first, while cum laude is between a 2:1 and a 1st, and summa cum laude a high first.
I thought Australia had a relatively similar system for honours degrees, but had simple percentages for ordinary bachelors degrees?