An average answers a different question
A simple average gives each number you include the same kind of treatment. The NSW ATAR process instead uses an aggregate of scaled marks in eligible courses. It includes the best two units of English and the best eight units from the remaining eligible units, then uses that aggregate to rank ATAR-eligible students.
This means the ATAR is neither the mean of every HSC mark on your record nor a direct conversion from one subject mark.
Why scaling changes the comparison
A mark of 85 in one course is not automatically equivalent to 85 in another for ATAR purposes. UAC scales raw HSC marks so results from different course combinations can be aggregated. Which marks contribute also depends on the 10-unit rule and course eligibility.
A high HSC average can therefore produce a different ATAR position from another student with the same average but a different course pattern and relative performance.
Read your HSC and ATAR as separate summaries
Use your course marks and performance bands to understand results in each subject. Use the ATAR to understand your position relative to the relevant age group in NSW. If you are comparing two results, compare the same measure and check whether selection adjustments or prerequisites apply to the university course you are considering.
Sources and editorial notes
Founder of ATAR Forecast. These guides explain school ranks, HSC results and the assumptions behind the forecasting tool, with links to NESA and UAC sources. These guides explain the process; NESA and UAC remain the official authorities.
- UAC: how your ATAR is calculated
- UAC: what the ATAR means
- UAC: report on the scaling of the 2025 NSW HSC
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An experimental estimate, not an official ATAR calculation.