How Does HSC Scaling Work? From HSC Marks to ATAR

You get 90 in HSC Physics. Your friend gets 90 in Business Studies. Will those marks contribute exactly the same amount to your ATAR?

Not necessarily. The two marks tell you how well each student met the standards of their course, but they don’t necessarily represent the same level of achievement relative to students across NSW.

HSC scaling is the process UAC uses to make results from different courses comparable. UAC examines how students in each course perform across all their HSC courses, adjusts the distribution of marks, and uses the resulting scaled marks to calculate ATARs.

The important part is that scaling isn’t a fixed bonus for taking a difficult subject. Your position within a course, the performance of its students across their other courses, and the distribution of marks all matter.

01Three different processes people call ‘scaling’

Before looking at UAC’s calculations, we need to separate three processes that are often confused.

These processes are connected, but they solve different problems.

1. School assessment moderation: making school marks comparable

Imagine two schools assessing the same Physics course.

At School A, the highest internal assessment mark is 95. At School B, the highest is 82.

Does that mean School A has stronger Physics students?

Not necessarily. School A might have set easier assessments, or School B might have marked more strictly.

NESA uses each school’s performance in the common HSC examination to moderate its school assessment marks.

The process preserves students’ school assessment rank order and reflects the relative differences between their assessment performances. It adjusts the group’s marks using the group’s examination results.

Importantly, you keep your own examination mark. The student ranked first internally doesn’t automatically receive the highest examination mark.

For most examined HSC courses, your reported HSC mark is calculated from:

\[ H=\frac{E+A}{2} \]

Here:

• \(H\) is your reported HSC mark before final rounding.
• \(E\) is your aligned HSC examination mark.
• \(A\) is your moderated school assessment mark, expressed on the reporting scale.

For example, an examination mark of 92 and a moderated assessment mark of 86 produce an HSC mark of 89.

Moderation helps make school assessment marks fair across schools. It isn’t UAC scaling.

NESA explains the process in its official assessment moderation guide.

2. HSC alignment: measuring achievement against standards

Suppose an HSC examination is unusually difficult.

A student might obtain a raw examination mark of 78 but demonstrate work that meets the Band 6 standard.

NESA doesn’t simply declare that 78 is a Band 5 result.

Instead, it uses standards-setting procedures to determine the raw examination mark required to meet each performance band. Those boundaries are then aligned with the HSC reporting scale.

For a two-unit course, the Band 6 boundary is reported as 90.

That doesn’t mean every student needs exactly 90% of the raw examination marks to achieve Band 6. The raw cut-off can vary.

Alignment therefore answers:

What standard of achievement did this student demonstrate?

It doesn’t answer:

How should this mark compare with results from entirely different subjects when calculating an ATAR?

That’s UAC’s job.

NESA’s explanation of HSC results and alignment covers the standards-setting process.

3. UAC scaling: making different courses comparable

UAC receives underlying raw HSC results from NESA and uses them in a separate scaling process.

It doesn’t simply take the aligned HSC marks printed on your results notice and add them together.

The outcome is a set of scaled marks on a common basis. These are used to calculate your ATAR, but individual scaled marks aren’t reported to students.

02How UAC scaling works

Think about two sporting competitions.

You finish fifth in one competition. Someone else finishes fifth in another. Which result is more impressive?

You need to know something about the standard of each competition. Fifth place among highly accomplished competitors may represent a different level of performance from fifth place among beginners.

HSC courses create a similar comparison problem.

But UAC has an advantage that our sporting example doesn’t: students take several courses, and their performances across those courses provide information about the academic achievement of each course’s candidature.

The analogy has a limit. UAC doesn’t simply rank courses as strong or weak, then award bonus marks. It uses a mathematical scaling process based on the achievement patterns and distributions of results across courses.

Why the students taking a course matter

Imagine two fictional HSC courses.

In Course A, many students achieve strong results across their other subjects.

In Course B, students’ results across their other subjects are more mixed.

If you perform well in Course A, you’re competing within a group that generally achieves strongly across the HSC.

UAC accounts for these differences when establishing the scaled marks for each course.

In particular, it adjusts the mean (average) and distribution of marks using information about the performance of the students taking that course across all their courses.

A course with a strong candidature generally has a higher scaled mean.

But that doesn’t mean every student in it automatically receives a high scaled mark.

A hypothetical dataset: the same HSC mark, different scaled marks

Consider these completely fictional results from two imaginary two-unit courses.

All marks and means in the last two rows are expressed on a two-unit scale out of 100.

The numbers are invented to illustrate UAC-style outcomes. They aren’t real HSC data, and the student’s scaled marks cannot be calculated from the other rows alone. UAC’s actual scaling method needs considerably more information.

Both students have a reported HSC mark of 90 and are at the 80th percentile within their respective courses. That means each performed better than approximately 80% of the candidates in their course.

Yet their hypothetical scaled marks differ.

Course A has the stronger candidature overall, reflected in its higher scaled mean. The individual student’s position within that candidature then contributes to their scaled result.

The student in Course A receives 83 scaled marks, while the student in Course B receives 72.

That is an 11-mark difference in their two-unit contributions to the ATAR aggregate, despite identical reported HSC marks.

Why scaling isn’t a fixed bonus

It would be tempting to interpret that example as saying Course A receives a scaling bonus of 11 marks.

That’s wrong.

Scaling isn’t:

\[ S=H+b \]

where \(S\) is a scaled mark, \(H\) is a reported HSC mark, and \(b\) is a fixed bonus.

A student’s scaled mark depends on their underlying performance and the scaling distribution for that course.

Two students with different marks in the same course won’t necessarily experience the same numerical difference between their HSC marks and scaled marks.

Scaling also preserves the ordering of students within a course based on their underlying marks. It doesn’t turn a lower-ranked performance into a higher-ranked performance within that course.

This is why a course with a high scaled mean can still produce low scaled marks for students who perform poorly within it.

It also explains why course difficulty alone doesn’t determine scaling.

Mathematics Extension 2 and Physics have traditionally had high scaled means because their students generally perform strongly across their HSC courses. UAC isn’t awarding extra marks simply because those syllabuses are challenging.

03From scaled marks to your ATAR

Once UAC has calculated scaled marks, it combines the appropriate ten units to produce an aggregate.

For the standard NSW ATAR, the calculation uses:

• Your best two units of English.
• Your best eight remaining eligible units.

An ordinary two-unit course contributes a scaled mark out of 100. A one-unit course contributes on a scale out of 50, subject to special rules for certain extension courses.

The maximum theoretical ten-unit aggregate is 500.

UAC then ranks eligible students using their aggregates and determines their ATARs in relation to the relevant NSW age cohort.

Your aggregate isn’t your ATAR.

For example, an aggregate of 400 out of 500 doesn’t mean an ATAR of 80.00.

The ATAR is a rank, not the percentage of marks you obtained.

04Does scaling change every year?

Yes.

UAC calculates course scaling using the performance of the students in the relevant HSC year.

A course doesn’t have one permanent conversion from an HSC mark to a scaled mark.

For example, you cannot assume that an HSC mark of 85 in Physics in 2026 will produce the same scaled mark as an HSC mark of 85 in Physics in 2025.

Even within one year, the reported HSC mark is rounded and aligned to standards, while UAC uses underlying raw results. There generally isn’t a unique scaled mark for every reported HSC mark.

That is why historical scaling tables are useful for understanding patterns but cannot guarantee an individual result.

As at 7 November 2026, UAC’s latest published annual scaling report is for the 2025 HSC. The final scaling outcomes for the 2026 HSC cohort are not yet available.

UAC’s ATAR Compass uses historical scaling information to estimate ATARs, rather than calculating the future year’s actual scaling.

Treat an estimate as an estimate.

05What scaling does and doesn’t depend on

A few distinctions help when interpreting advice about scaling.

Does going to a high-performing school help your scaling?

UAC doesn’t include your school’s name, ranking, or reputation in its ATAR calculation.

However, school assessment moderation uses your school-course group’s examination performance. That is a separate process, and it means your school assessment context matters before UAC receives the marks.

The difference between those two processes is explored further in Does Your School Affect Your ATAR? NSW HSC Explained.

Do university prerequisites affect scaling?

No. Entry requirements and scaling are different systems.

For students completing the HSC in 2026 and considering university entry in 2027, requirements depend on the institution and degree.

For example, the University of Sydney’s mathematics prerequisite policy specifies Mathematics Advanced Band 4, or Mathematics Extension Band E3, for certain courses.

By contrast, UNSW explains that it uses assumed knowledge rather than formal school-subject prerequisites. Students who don’t have the assumed knowledge may still be considered for admission but could need additional preparation.

These are university requirements or recommendations, not universal NESA prerequisites for enrolling in HSC subjects.

Schools also have their own course offerings, timetables, and subject-selection procedures. Those administrative decisions are separate from the statewide ATAR calculation.

Check the entry requirements for your exact university degree and entry year rather than treating a subject recommendation as a statewide rule.

06Questions and solutions

The following questions use hypothetical results. All scaled marks are invented for practice and should not be treated as predicted HSC scaling outcomes.

Question 1

A student has completed six two-unit ATAR courses and is eligible for an ATAR.

Their scaled marks are:

Calculate their ten-unit aggregate and identify the course that won’t contribute.

Solution 1

The aggregate is 360, with Biology excluded.

The student must include their two English units, worth 63 scaled marks.

From the other five courses, the strongest four two-unit contributions are Modern History (79), Mathematics Advanced (77), Physics (73), and Geography (68).

Using \(G\) for the aggregate:

\[ \begin{aligned} G&=63+79+77+73+68\\ &=360 \end{aligned} \]

Biology has the lowest remaining scaled contribution, so it is omitted.

The tempting mistake is to average all six results or simply take the five highest marks, which might exclude English. Neither follows the ATAR rules.

The aggregate is 360 out of 500. It cannot be converted directly into an ATAR percentage.

Question 2

Two students, Alex and Blake, complete the same HSC Physics course at the same school.

Alex is ranked first internally. Blake is ranked second.

At the end of the HSC, their reported components are:

Assume standard averaging applies, with no special examination adjustments.

(a) Calculate each student’s reported HSC mark.

(b) Explain why Blake can receive a higher final HSC mark despite having a lower internal assessment rank.

(c) A classmate claims that Alex must receive a higher scaled mark because Alex ranked first internally. Explain why this conclusion is unjustified, and identify what information would be needed to calculate the exact UAC scaled marks.

Solution 2

(a) Blake’s reported HSC mark is 89, while Alex’s is 86.

Using \(H=(E+A)/2\), where \(E\) is the aligned examination mark and \(A\) is the moderated assessment mark:

For Alex:

\[ \begin{aligned} H_A&=\frac{79+93}{2}\\ &=86 \end{aligned} \]

For Blake:

\[ \begin{aligned} H_B&=\frac{95+83}{2}\\ &=89 \end{aligned} \]

(b) Blake’s stronger examination performance outweighs Alex’s advantage in the moderated school assessment.

NESA moderation preserves the school assessment rank order, so Alex retains the higher moderated assessment mark.

But each student keeps their own examination result.

Blake earned 95 in the examination, while Alex earned 79. Blake’s stronger examination performance produces the higher final HSC mark.

(c) Alex’s higher internal assessment rank doesn’t guarantee a higher scaled mark.

UAC scales the underlying raw HSC results for the course, not the internal assessment rank alone.

Scaling preserves the order established by those underlying results, but it doesn’t award the school’s first-ranked student a separate bonus.

To calculate exact scaled marks, we would need the relevant raw HSC results and UAC’s scaling information for that year’s Physics candidature. The displayed marks alone aren’t enough.

The misconception is treating school assessment moderation and UAC scaling as the same process.

They are not.

Question 3

Two fictional students complete the same HSC year. Each has exactly ten eligible ATAR units.

Their first eight units have identical scaled contributions:

Their remaining two-unit course differs.

Student A completes Physics, receiving a reported HSC mark of 84 and a scaled mark of 82.

Student B completes Business Studies, receiving a reported HSC mark of 94 and a scaled mark of 74.

(a) Calculate each student’s aggregate.

(b) Explain how the student with the lower reported HSC mark in their final course can nevertheless have the higher aggregate.

(c) Can the difference between their actual ATARs be calculated from this information?

Solution 3

(a) Student A has an aggregate of 385, while Student B has an aggregate of 377.

Student A:

\[ \begin{aligned} G_A&=68+81+78+76+82\\ &=385 \end{aligned} \]

Student B:

\[ \begin{aligned} G_B&=68+81+78+76+74\\ &=377 \end{aligned} \]

Student A’s aggregate is eight scaled points higher.

(b) The reported HSC marks belong to different courses and aren’t directly comparable for ATAR purposes.

The Physics result contributes 82 scaled marks, while the Business Studies result contributes 74.

Those are stipulated hypothetical UAC outcomes reflecting the separate course scaling distributions.

Although Student B’s reported HSC mark is ten marks higher, Student A contributes eight more scaled marks.

That is why the reported HSC mark alone cannot determine which course contributes more to an aggregate.

(c) We cannot calculate the exact ATAR difference.

Because both students are in the same HSC year, Student A’s higher aggregate means Student A cannot have a lower ATAR on the ordinary aggregate ranking calculation.

However, ATAR values depend on the statewide aggregate distribution and are reported in increments of 0.05.

The students might receive different ATARs, or the published ATARs could be equal after rounding.

Eight additional aggregate points don’t represent a fixed number of ATAR points.

Question 4

A student satisfactorily completes the following courses in the same HSC year and meets the ATAR eligibility requirements.

All results below are hypothetical scaled contributions, not reported HSC marks.

The student has completed Mathematics Extension 1 and Mathematics Extension 2, so the special two-unit weighting applies to Mathematics Extension 1.

(a) Determine which mathematics results are available for inclusion.

(b) Calculate the student’s ten-unit aggregate.

(c) Explain why simply choosing the five largest numbers from the table would produce an incorrect result.

Solution 4

The correct aggregate is 398, and Mathematics Advanced is excluded despite its scaled result of 96.

(a) Mathematics Extension 1 and Mathematics Extension 2 are available for inclusion.

When Mathematics Extension 2 is completed, Mathematics Advanced isn’t included in the ATAR calculation.

Mathematics Extension 1 counts as two ATAR units, so its one-unit scaled result is doubled:

\[ 2(43)=86 \]

Thus, the available mathematics contributions are:

• Mathematics Extension 1: 86 across two ATAR units.
• Mathematics Extension 2: 83 across two units.

Mathematics Advanced’s 96 cannot be selected.

(b) Include English and choose the best eight remaining units.

English Advanced contributes 70.

The remaining eligible two-unit contributions are Mathematics Extension 1 (86), Mathematics Extension 2 (83), Physics (82), Chemistry (77), and Biology (72).

Select the four highest.

\[ \begin{aligned} G&=70+86+83+82+77\\ &=398 \end{aligned} \]

Biology is excluded from the selected ten units.

(c) The largest reported or displayed numbers cannot simply be selected without checking eligibility and unit weighting.

Mathematics Advanced’s high result is irrelevant to this ATAR calculation because of the Mathematics Extension 2 rule.

Mathematics Extension 1’s one-unit scaled mark must also be doubled because it counts as two units in this combination.

Finally, English must contribute at least two units.

All three conditions need to be applied before comparing eligible contributions.

A strong result in a course that cannot be selected doesn’t override UAC’s course-combination rules.

Question 5

An adviser is comparing two fictional two-unit courses, A and B.

Both courses have exactly four candidates. The candidates in each course have identical underlying raw course marks of 60, 70, 80, and 90.

UAC’s hypothetical summary statistics give:

You know that scaling preserves the ordering of students within each course.

Two ATAR-eligible students are being compared. One achieved the highest raw mark of 90 in Course A; the other achieved the highest raw mark of 90 in Course B.

Each student has eight other included ATAR units, including English, contributing exactly 300 scaled points in total. Their remaining two units come from Course A or Course B, respectively.

The adviser claims:

“Course A has the higher scaled mean, so its highest-ranked student must receive the higher scaled mark and the higher aggregate.”

Your task is to determine whether the claim is logically guaranteed by the supplied information.

(a) Construct one possible set of four ascending scaled marks for each course that satisfies the given means and makes Course A’s top student receive the higher scaled mark.

(b) Construct a different set satisfying exactly the same given means and rank ordering, but making Course B’s top student receive the higher scaled mark.

(c) Calculate the two students’ aggregates under both constructions.

(d) Explain what this tells us about using course scaled means to predict individual results, and why your constructions aren’t exact simulations of UAC’s real scaling algorithm.

All scaled marks in your constructions must be between 0 and 100, strictly increase with raw-mark rank, and have the stated arithmetic mean.

Treat this as a mathematical problem about whether the supplied information determines the answer, not as a reconstruction of UAC’s full scaling procedure.

Solution 5

The adviser’s claim is not guaranteed. A higher scaled mean does not, by itself, determine the scaled mark received by the highest-ranked student.

We can prove this by constructing two different sets of results that satisfy every stated numerical constraint but produce opposite outcomes.

(a) First construction: Course A’s top student scores higher.

Consider these hypothetical scaled marks:

The arithmetic mean for Course A is:

\[ \begin{aligned} \bar S_A&=\frac{50+60+70+80}{4}\\ &=65 \end{aligned} \]

The mean for Course B is:

\[ \begin{aligned} \bar S_B&=\frac{45+55+65+75}{4}\\ &=60 \end{aligned} \]

Here, \(\bar S\) represents the mean scaled mark.

Both sets preserve the students’ rank ordering.

The top student in Course A receives 80, while the top student in Course B receives 75.

Course A’s top student is ahead by five scaled marks.

(b) Second construction: Course B’s top student scores higher.

Now consider:

Check Course A’s mean:

\[ \begin{aligned} \bar S_A&=\frac{57+62+69+72}{4}\\ &=65 \end{aligned} \]

Check Course B’s mean:

\[ \begin{aligned} \bar S_B&=\frac{30+50+65+95}{4}\\ &=60 \end{aligned} \]

Both means are unchanged.

Both sets are still strictly increasing, so no student’s rank has been reversed.

But now Course B’s top student receives 95, while Course A’s top student receives 72.

The winner has reversed.

(c) Calculate the aggregates.

Each student already has 300 scaled points from eight other included units.

In the first construction:

\[ \begin{aligned} G_A&=300+80=380\\ G_B&=300+75=375 \end{aligned} \]

Course A’s student has the higher aggregate.

In the second construction:

\[ \begin{aligned} G_A&=300+72=372\\ G_B&=300+95=395 \end{aligned} \]

Course B’s student has the higher aggregate.

The two constructions satisfy the same supplied means and rank-order constraints, yet they produce opposite aggregate rankings.

Therefore, the information given is insufficient to establish which student must have the higher aggregate.

(d) The missing information is the distribution of scaled marks, not just the mean.

A mean describes the centre of a distribution.

It doesn’t uniquely describe how spread out the marks are, how strongly the top students perform, or how results change across the different positions in a course.

In the second construction, Course B has a lower mean but a much greater spread. Its highest-ranked student can therefore have a higher scaled mark.

That is the key conceptual point: a course’s scaled mean isn’t an individual student’s scaling bonus.

The mathematical constructions demonstrate why a mean and a ranking alone don’t determine the top student’s score.

They don’t demonstrate that UAC would actually assign either set of marks. UAC also uses candidates’ results across their other courses, the course’s full distribution, its spread, and further technical constraints.

Our invented lists are counterexamples to an unsupported inference, not substitutes for the actual scaling algorithm.

The same reasoning explains why a subject’s historical scaled mean cannot tell an individual student exactly what they’ll receive.

Even knowing that one course has a stronger candidature overall doesn’t tell you every detail of its scaling distribution.

And even after the scaled marks are known, translating aggregates into actual ATAR values requires the relevant year’s statewide ranking information.

07What should you take from scaling when preparing for the HSC?

For the 2026 HSC cohort, the useful distinction is between the results you can influence and the scaling statistics you cannot control.

You can improve your understanding, examination performance, assessment performance, and position within a course.

You cannot control the statewide candidature or know in advance exactly how UAC will scale the year’s marks.

The next practical concept is your position within each course. When reviewing a trial examination, don’t just ask whether your mark sounds high. Look at the questions you lost marks on, what those errors reveal, and which improvements would move your performance towards the stronger end of that course.

Scaling then provides the mechanism for comparing that achievement with results from other courses. It doesn’t replace the achievement itself.

For the applicable eligibility rules and calculation methods, refer to UAC’s ATAR eligibility requirements and ATAR calculation guide. These were checked on 7 November 2026 for the 2026 HSC cohort; students completing later HSC years should check the rules applying to their own cohort.