How the HSC ATAR is calculated

Every course gives you two marks: an examination mark from the external HSC exam, and a school-based assessment mark. NESA moderates the school mark against your school's exam performance so that assessment marks are comparable between schools, then averages the moderated assessment mark and the examination mark to produce your HSC mark. That HSC mark, out of 100 for a 2-unit course, is what appears on your record of achievement.

• You must complete at least 10 units of ATAR courses, including at least 2 units of English.
• The old Category A and Category B distinction was removed from the 2025 HSC onwards, so VET and other formerly Category B courses now count like any other ATAR course.
• Courses must be completed at the HSC level: Year 11 preliminary results do not contribute.

UAC does not use HSC marks directly. It first scales every course so that marks reflect the strength of the students who took each course. The result is a scaled mark out of 50 per unit, so a 2-unit course yields a scaled mark out of 100.

Scaling is recalculated every year from the actual cohort. UAC publishes summary statistics for each course in its annual scaling report but, unlike Victoria, it does not publish a mark-by-mark scaling table. Any NSW calculator therefore has to model each course's curve from those summaries, which is why estimates are indicative rather than exact.

Your aggregate is the sum of scaled marks for 10 units: your best 2 units of English, which are compulsory, plus your best 8 remaining units. The maximum aggregate is 500.

• Units are selected unit by unit, so a single unit of a 2-unit course can count on its own if that is the best combination.
• If you take both Mathematics Extension 1 and Extension 2, each counts as 2 units.
• Extra units beyond 10 do not add anything. They can only help by displacing a weaker unit.

UAC then ranks every aggregate against the whole NSW age cohort, including those who left school before Year 12, to produce the ATAR. It runs from 99.95 to 30.00 in 0.05 steps.

A student takes English Advanced (2 units), Mathematics Advanced (2), Biology (2), Modern History (2), Business Studies (2) and Studies of Religion I (1 unit): 11 units in total.

1. Each course is scaled to a mark out of 50 per unit. Suppose English Advanced scales to 84 out of 100, Mathematics Advanced 80, Biology 72, Modern History 76, Business Studies 68 and Studies of Religion I 33 out of 50.
2. English Advanced's 2 units (84) are locked in.
3. The best 8 of the remaining 9 units are chosen unit by unit: Mathematics 80, Modern History 76, Biology 72, Business Studies 68 (8 units). The 1-unit Studies of Religion result (33 out of 50) is lower per unit than any of those, so it is left out.
4. Aggregate = 84 + 80 + 76 + 72 + 68 = 380 out of 500.
5. UAC ranks 380 against the cohort. In recent years an aggregate around 380 has corresponded to an ATAR in the high 80s.

• The school assessment mark is half of every HSC mark and is moderated by your school's exam results, so consistent effort across the year matters as much as the final exam.
• Your English mark always counts, so it is never a subject to coast in.
• A weak 2-unit course drags harder than a weak 1-unit course. If you are choosing what to prioritise, look at the units, not just the subject.