HSC scaling explained, with 2025 data
7 min read ยท updated 2026-10-02
Scaling is how UAC turns HSC marks in very different courses into numbers that can be added together for the ATAR. It does not punish or reward subjects; it adjusts for how strong each course's students are. Here is how it works, using the 2025 figures.
How the ATAR is built
The ATAR is calculated from scaled marks in 10 units of ATAR courses: the best 2 units of English plus the best 8 units from the rest. To be ATAR-eligible, a student must complete at least 10 units of ATAR courses, including 2 units of English, three courses of 2 units or more, and four subjects. From 2025 there is no longer a Category A requirement.
Scaling estimates each course's marks on a common scale, based on how its students performed across all their courses. A course taken by students who do well everywhere scales up; a course whose students do less well overall scales down.
Scaled means in 2025 (per unit, out of 50)
Mean HSC mark first, then mean scaled mark, from UAC's 2025 report:
- โ Mathematics Extension 2: HSC mean 41.5, scaled mean 43.4
- โ Mathematics Extension 1: 39.7, scaled 39.7
- โ English Extension 1: 42.8, scaled 36.1
- โ English Advanced: 41.1, scaled 32.8
- โ Chemistry: 37.6, scaled 32.0
- โ Mathematics Advanced: 39.6, scaled 31.9
- โ Economics: scaled 31.4
- โ Physics: 37.0, scaled 31.0
- โ Biology: 36.7, scaled 26.2
- โ Legal Studies: 37.8, scaled 25.3
- โ Business Studies: 37.4, scaled 23.9
- โ Mathematics Standard 2: 36.0, scaled 23.3
- โ English Standard: 36.0, scaled 20.4
What this means for subject choice
UAC is clear that the table should not be read as a simple conversion: each HSC mark covers a range of raw marks and scaled marks. The practical lesson is that a high mark in any course helps, and that students should choose subjects they can do well in. A weak result in a high-scaling course can still contribute less than a strong result in a lower-scaling one.
FAQs
Which HSC subjects scale best?๏ผ
In 2025, Mathematics Extension 2 had the highest scaled mean of the large courses (43.4 out of 50 per unit), followed by Mathematics Extension 1 (39.7).
Does English count towards the ATAR?๏ผ
Yes. The best 2 units of English must be included, plus the best 8 units from other courses.
Should my child pick subjects for scaling?๏ผ
Only alongside ability and interest. A strong mark in a subject your child is good at usually beats a weak mark in a higher-scaling one.
Sources
Facts on this page were checked against these official sources on 2026-10-02.
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