ATAR Calculation Worked Example
A worked example using NSW HSC rules illustrates how the ATAR is derived from raw subject performance. Student profile: studying English Advanced (2 units), Mathematics Extension 1 (3 units, counting as 2-unit base + 1 extension), Mathematics Extension 2 (1 unit), Chemistry (2 units), Physics (2 units), and Biology (2 units) — total: 12 units available. Step 1: calculate HSC marks for each subject (50% school assessment + 50% exam mark). Example: English Advanced raw HSC mark = 78. Mathematics Extension 1 raw HSC mark = 85. Chemistry raw = 82. Physics raw = 88. Biology raw = 74. Step 2: scale each mark according to the current year's scaling tables. Approximate scaling: English Advanced 78 → scaled 76. Maths Extension 1 85 → scaled 92. Chemistry 82 → scaled 86. Physics 88 → scaled 93. Biology 74 → scaled 72. Step 3: sum the best 10 units. With Extension 1 (1 unit) and Extension 2 (1 unit) counting separately: best 10 units from available scaled marks. Drop Biology (lowest scaled: 72). Include Extension 1 (92) and Extension 2 (separate scaling). Step 4: the aggregate score is converted to ATAR percentile using that year's percentile tables. Important: this example uses approximate scaling values — actual scaling changes every year and is published by BOSTES (NSW) after the HSC exam. The calculation principles are consistent; the specific scaling values vary.