The HSC scaling report is the official document the Universities Admissions Centre (UAC) publishes each year to explain exactly how HSC marks were converted into the scaled marks that build an ATAR. It is the only public source of real scaling data for NSW, and almost every “best scaling subjects” list you have ever read is someone’s summary of one table inside it. Learning to read it yourself takes about ten minutes and will save you from a lot of confident nonsense on student forums.
At NextStepAcademy we work through this report with Year 10 and Year 11 families every subject selection season, because it answers the question parents actually care about: not “which subject scales best” but “what does scaling do to my child’s marks, and how much should it change what they choose”.
What is the HSC scaling report?
It is a report titled Report on the Scaling of the NSW Higher School Certificate, produced by UAC for each HSC year. The current edition covers the 2025 HSC. It sets out the scaling method, reports results for that year’s cohort, answers common student questions, and finishes with an appendix of nine data tables covering every course with a large enough candidature.
The report is free and downloadable from the UAC publications page. There is no paywall and no secret version. Everything the tutoring industry knows about HSC scaling comes from this document.
Who publishes the scaling report and when does it come out?
UAC publishes two things each cycle. A short preliminary report appears first, around the time ATARs are released in December, and gives the headline picture for that year. The full report, with the complete appendix of tables, follows in the new year. That means the most detailed data available to a student choosing subjects in Term 3 is always from the previous HSC cohort, which is exactly what you want, because it is the most recent completed year.
One consequence worth understanding: nobody, including UAC, can tell you in advance what a subject will scale to in your year. Scaling is calculated after the exams from the cohort that sat them. Past reports show relativities that are quite stable year to year, but they are not a forecast.
What does scaling actually do to your HSC marks?
Scaling does not reward or punish subjects. It puts every course onto a common scale so that students who took different combinations can be compared fairly. If one course is taken by a group who, on average, perform strongly across all of their other courses, that course ends up with a higher scaled mean.
The key sentence in the report is that the scaled mean of a course equals the average academic achievement of the students who took it, measured by their average scaled mark across every course they completed. Scaling measures the company you keep, not the difficulty of the syllabus. Our explainer on how HSC scaling impacts your ATAR works through that idea in more detail.
Which marks does UAC actually scale?
This trips up almost everyone. UAC does not scale the HSC mark printed on your Record of Achievement. It scales your raw HSC mark, which is the average of your raw examination mark and your raw moderated school assessment. Those raw marks are never reported to students.
Before the algorithm runs, marks in every course are standardised to a mean of 25 and a standard deviation of 12 on a one-unit basis. So the numbers you see in the report do not line up with the numbers on your results notice, and they were never meant to.
What is a scaled mean and why does it matter?
The scaled mean is the average scaled mark of everyone who completed that course, out of 50 per unit. It is the single number people are quoting when they say a subject “scales well”. A course with a scaled mean of 32 had a candidature that was, on average, academically stronger across all their subjects than a course with a scaled mean of 22.
What it is not is a promise. A scaled mean of 32 does not mean you will get 32. Your scaled mark depends on where you sit within that course’s candidature.
How do you read Table A3?
Table A3 is the table everyone quotes. For each course it gives two rows, one for HSC marks and one for scaled marks, and for each it reports the number of students, the mean, the standard deviation, the maximum mark, and the 99th, 90th, 75th, 50th and 25th percentiles.
Reading across a single row is where the value is. Take Ancient History in the 2025 report: 7,495 students, a mean HSC mark of 36.4 and a mean scaled mark of 22.4, with the 90th percentile of scaled marks at 44.4. That last figure is the useful one. It says a strong Ancient History student was still scaling into the mid 40s out of 50, well above the course mean.
The other tables are worth knowing about. Table A1 gives course enrolments, gender split, ATAR eligibility and the maximum ATAR achieved by anyone in that course. Table A2 shows the distribution of HSC marks by course. Tables A4 and A5 compare two consecutive years, which is how you check whether a shift is a trend or noise. Table A6 lists the courses that actually contributed to students’ ATARs.
What did the big HSC courses scale to in 2025?
Here is the shape of Table A3 for ten of the largest courses, taken directly from the 2025 report.
The spread from roughly 20 to 43 looks dramatic, and it is the reason scaling talk dominates subject selection conversations. But notice what the top of that list has in common: Mathematics Extension 2, Mathematics Extension 1 and English Advanced are all courses taken disproportionately by students carrying strong marks in everything else. For a fuller picture see our guides to the highest scaling HSC subjects and the worst scaling HSC subjects.
Why can’t you use the report as a conversion table?
UAC states plainly that Table A3 should not be used as a simple HSC to scaled mark conversion table, and the reason is worth understanding. Behind a single reported HSC mark there can be a range of raw marks, and therefore a range of scaled marks. Two students with the same HSC mark in the same course can finish with different scaled marks.
So when a forum post tells you “an 85 in Business Studies becomes a 74”, that number is invented. The report does not support that arithmetic, and neither do ATAR calculators that claim to do it.
How are extension courses scaled differently?
Extension courses are not scaled on their own candidature in the same way. Their scaled means and standard deviations are determined by how the extension students performed in the corresponding two-unit course. History Extension is a special case, since it can be taken by both Modern History and Ancient History students, and Science Extension is another, since its students may be doing up to three two-unit science courses.
That is why extension courses cluster near the top of the table, and why a post like our look at whether Science Extension scales well has to explain the mechanism rather than just quote a number.
What should the report change about your subject choices?
Less than you think, and more than nothing. Here is the honest reading, based on what we see with students every year.
- A weak mark in a high-scaling course beats nothing, but not much. Scaling lifts the top of a strong candidature far more than the bottom.
- Units matter more than most students realise. In 2025, 53.0 per cent of students completed exactly 10 ATAR units, so for most students every unit counted.
- Interest predicts marks. A student who finishes the year engaged will out-perform the same student grinding through a subject they resent, and that difference is usually larger than the scaling gap they were chasing.
Our full HSC subject selection guide and the ATAR calculation guide cover how these trade-offs play out across a full pattern of study.
An illustrative example
Consider two Year 11 students, both sitting around a Band 5 standard. Student A takes Mathematics Advanced because she enjoys it and finishes in the top quarter of that candidature. Student B takes it purely because of the scaled mean, disengages by Term 2 of Year 12, and finishes in the bottom quarter. They chose the same “well scaling” subject. The report’s percentile columns show why their scaled marks land nowhere near each other: the 75th and 25th percentiles of a course are separated by a very large gap. This example is illustrative rather than a specific student, but the pattern is the one we see most often.
Frequently asked questions
Where can I download the HSC scaling report?
From the UAC website, in the publications section. The current full edition is the Report on the Scaling of the 2025 NSW Higher School Certificate, and past years going back decades are also available.
Does the scaling report tell me what my ATAR will be?
No. It explains the process and reports the previous cohort’s results. Your ATAR depends on your own scaled marks in your best 10 units and how those compare with the rest of the state.
Do the scaling numbers change much from year to year?
Course relativities are generally stable, which is why Tables A4 and A5 present two years side by side. Small movements are normal. A course does not usually jump several points without a change in who is taking it.
Is an ATAR of 99.00 the top one per cent?
Not of the ATAR cohort. UAC reports that 1.8 per cent of the 2025 ATAR cohort gained an ATAR of 99.00 or above. The ATAR is scaled against all HSC-aged people in NSW, not only those who sat the HSC.
Should my child choose subjects based on scaling?
Scaling should be one input, not the deciding one. Ability, interest, prerequisites for university courses and the teaching strength at the school all matter, and in our experience they move a final ATAR more than a two-point difference in a scaled mean does.
Getting help making the call
If your family is weighing up subject choices or your child is trying to lift their position within a course rather than swap out of it, a tutor who knows the NSW system can make the conversation a lot shorter. Our HSC tutoring in Sydney team works with students across every HSC subject area, in home and online.
Book your first lesson today and see the difference a specialist HSC tutor makes. If you do not love the first lesson, you do not pay for it.