Every year, students choosing their A-Levels ask a version of the same question: "Which science is the hardest?" It's the wrong question. The right question is: which science has the least forgiving grade boundaries?
A subject can have a hard paper and low boundaries, making top grades accessible with solid performance. Or it can have a moderately hard paper but a compressed boundary structure — where every mark between E and A* is fiercely contested. The latter is genuinely more demanding, regardless of perceived difficulty.
We analysed official AQA A-Level grade boundaries for Biology, Chemistry, and Physics from 2022 to 2025. All three sciences are marked out of 200 total raw marks, making a direct comparison meaningful.
The 2025 verdict at a glance
Biology
Chemistry
Physics
AQA A-Level, June 2025. All subjects out of 200 total marks.
The "forgiveness gap": A* to E spread
The most useful metric for comparing difficulty is the spread between the A* boundary and the E boundary. A wide spread means a fail and an A* are far apart in raw marks — there's more room to move up the grade scale with additional marks. A narrow spread means every mark counts more acutely.
A* to E boundary spread (raw marks) — 2022 to 2025
Biology
Chemistry
Physics
A wider bar = more marks separate A* from E = more room to move between grades.
Full boundary comparison: 2022–2025
All subjects AQA, out of 200 total marks. Percentages shown in brackets.
| Subject | Year | A* | A | B | C | E |
|---|---|---|---|---|---|---|
| 🧬 Biology | 2022 | 143 (72%) | 126 (63%) | 106 (53%) | 87 (44%) | 49 (25%) |
| 2023 | 153 (77%) | 135 (68%) | 114 (57%) | 94 (47%) | 55 (28%) | |
| 2024 | 157 (79%) | 139 (70%) | 118 (59%) | 98 (49%) | 58 (29%) | |
| 2025 | 160 (80%) | 144 (72%) | 128 (64%) | 109 (55%) | 71 (36%) | |
| ⚗️ Chemistry | 2022 | 145 (73%) | 128 (64%) | 106 (53%) | 84 (42%) | 41 (21%) |
| 2023 | 157 (79%) | 139 (70%) | 115 (57%) | 91 (46%) | 44 (22%) | |
| 2024 | 160 (80%) | 143 (72%) | 118 (59%) | 93 (47%) | 43 (22%) | |
| 2025 | 163 (82%) | 147 (74%) | 132 (66%) | 110 (55%) | 66 (33%) | |
| ⚛️ Physics | 2022 | 140 (70%) | 122 (61%) | 100 (50%) | 79 (40%) | 37 (19%) |
| 2023 | 151 (76%) | 132 (66%) | 109 (55%) | 86 (43%) | 41 (21%) | |
| 2024 | 155 (78%) | 136 (68%) | 112 (56%) | 88 (44%) | 43 (22%) | |
| 2025 | 161 (81%) | 146 (73%) | 131 (66%) | 109 (55%) | 65 (33%) |
Source: AQA A-Level grade boundary documents, June 2022–2025.
What the data actually shows
Chemistry demands the highest raw marks for A*
In 2025, the AQA Chemistry A* boundary was 163 out of 200 — 81.5% of total marks. This was the highest A* boundary of the three sciences, edging out Physics (161) and Biology (160). Chemistry has consistently sat at the top of the A* threshold across all four years analysed. If you're targeting an A* in Chemistry, you have very little margin for error.
Physics has the most compressed spread at the top
Despite Physics having a slightly lower A* boundary than Chemistry, its grade spread from E to A* is the narrowest of the three — meaning the distance between a pass and top performance is smaller in raw mark terms. In 2025, the Physics A*-to-E spread was 96 marks, compared to 97 for Chemistry and 89 for Biology. Every mark in a Physics paper pushes you through the grade boundaries faster.
Biology is the most forgiving at lower grades
Biology's E boundary has historically been higher relative to the A* boundary than the other two sciences. In 2025, you needed 71 marks for an E in Biology — the highest E boundary of the three. This indicates a less compressed lower end, meaning students at the lower grade ranges have more raw marks separating each grade in Biology.
All three are converging upward
A striking trend across all four years: boundaries have moved consistently upward. The A* boundary for Chemistry rose from 145 in 2022 to 163 in 2025 — an increase of 18 marks in three years. Physics and Biology show similar trajectories. This suggests the student cohort's performance has improved, or papers have become more accessible, or both.
What this means when choosing your A-Levels
Chemistry if you're targeting top medicine/STEM
The high A* boundary means top performers are genuinely tested. If you consistently score over 80% in practice, Chemistry rewards precision and breadth. One underperforming paper matters significantly.
Biology if you prefer essay-based assessment
Slightly lower A* threshold and the more distributed boundary spread makes Biology marginally more accessible for students who perform well across topics rather than excelling in high-precision calculation.
Physics if you're strong in Maths
Physics' compressed grade spread means mathematical precision converts directly into grade improvements. If you score well in quantitative questions, the boundary structure rewards you. If you struggle with calculations, it amplifies the issue.
Taking all three? Chemistry is your limiting factor
Triple science students should treat Chemistry as the hardest boundary target and allocate revision time accordingly. Meeting Chemistry's A* boundary is the hardest of the three consistent objectives.
Check your A-Level grade from a raw mark
Enter your Biology, Chemistry, or Physics raw mark into the GradesNova A-Level calculator to see your grade under official 2025 AQA boundaries — with UCAS points included.
A-Level Grade Boundary Calculator →