How is my final degree classification calculated?
Your degree classification is based on your final average mean weighted mark (AMW), which is calculated as follows. For 3-year degrees (BSc) your Level 2 and Level 3 averages are weighted in the ratio 2:3. For 4-year degrees (MPhys/MSci) your Level 2, Level 3 and Level 4 averages are weighted in the ratio 2:3:4. There is a table showing Degree Class vs. Mark Range at https://www.dur.ac.uk/physics/students/assessment/. So for example a BSc student who gets an average of 50% in Level 2 and 70% in Level 3 will have a final AMW of 62%, which corresponds to an upper second class degree. Note: there are rules about the number of modules that you are allowed to fail and also about the seriousness of the fails, so even if you end up with a final AMW of, say, 60%, you may not be eligible for an honours degree.
Note that the University records module marks as integers, but AMW marks are recorded to two decimal places and are not rounded up or down. So, for example, if your final AMW mark works out to be 59.99 then this does not get rounded up to 60.