Chemistry is the subject where grade boundaries tend to surprise students most. Unlike Biology, where thresholds have been relatively stable, IGCSE Chemistry (syllabus code 0620) has shown some of the sharpest swings between sessions in recent memory — a 20-mark difference in the A* boundary between some June and November sittings. If you are preparing for the June 2026 examination, or advising students who are, understanding what those swings mean — and why they happen — is as important as knowing the numbers themselves. This guide gives you both.

All data in this guide is sourced directly from the official Cambridge International IGCSE grade threshold tables page , which publishes results for every subject and session. The individual PDFs referenced throughout — including the June 2025 Chemistry threshold table and the November 2025 Chemistry threshold table — are the primary sources for the figures in this analysis.

What are grade boundaries and how do they work in IGCSE Chemistry?

Cambridge International (CIE) publishes what it officially calls grade threshold tables after every examination series. These are the minimum total marks a student must score — after all three papers are combined and weighted — to be awarded each grade from G through to A*. For extended candidates sitting IGCSE Chemistry 0620, the standard paper combination is Paper 2 (Multiple Choice Extended, 40 marks, 45 minutes), Paper 4 (Theory Extended, 80 marks, 75 minutes), and Paper 6 (Alternative to Practical, 40 marks, 60 minutes). Cambridge labels this combination Option CY in its official threshold tables, and the three papers combine for a maximum weighted total of 200 marks.

There is one rule that every student and parent must understand before reading any further: Cambridge does not award A* at the level of individual papers. A* exists only at the level of the overall weighted total. There is no such thing as a Paper 4 A*. A student who achieves a perfect score on Paper 2 and Paper 6 but performs poorly on Paper 4 can still miss the A* boundary altogether. Knowing how the overall total is built across the three papers is the only way to plan effectively for an A* result.

As Cambridge's own awarding guidance explains, boundaries are set by reference to the actual performance of candidates in each sitting — not to a fixed percentage. This is why boundaries move between sessions and why comparing your score to a previous year's threshold is only meaningful once you understand the cohort context behind that number.

Why Chemistry boundaries fluctuate more than you might expect

One of the most striking things about the Chemistry 0620 data is how much the boundaries move between June and November. This is not random. Chemistry attracts a very particular cohort split between the two sessions. The June sitting is dominated by students completing the full two-year IGCSE cycle for the first time. November draws a much smaller candidature, heavily weighted toward retakers and a narrower group of school cohorts. Because Cambridge sets its boundaries by reference to the performance of the actual cohort in each sitting, those cohort differences translate directly into boundary differences — sometimes large ones.

This means the headline A* number in any given session is not just a measure of paper difficulty. It is also a signal about who sat that paper. As Cambridge International's own guidance on grade thresholds makes clear, the awarding process is designed to ensure that a student of a given ability receives the same grade regardless of which session they sit — which is precisely why boundaries must move when cohorts differ. Knowing that is essential context before drawing conclusions from the numbers below.

Session-by-session overview: what the overall boundaries show

For Option CY across the past three years, the A* boundary has ranged from 149 to 173 out of 200 — a spread of 24 marks. That is nearly double the spread seen in IGCSE Biology over the same period, and it makes Chemistry one of the most variable subjects in the IGCSE sciences suite in terms of boundary movement.

That November 2025 drop — from 173 to 153 in a single series — is worth pausing on. A fall of 20 marks is not evidence that the November paper was lenient. It reflects the smaller, differently composed candidature and Cambridge's awarding process responding to that. Students who see the 153 and think November is the easier route to A* are drawing the wrong conclusion from the data.

Paper-by-paper breakdown: minimum marks per grade

Paper 2 — Multiple Choice Extended (40 marks)

Paper 2 in Chemistry is 40 multiple choice questions sat in 45 minutes. It is binary — every question is right or wrong, there are no partial marks, and there is no penalty for an incorrect answer. The Chemistry Paper 2 has shown a more pronounced upward shift in its A boundary over this period, driven in part by the increasing accessibility of the extended multiple choice format to well-prepared candidates.

The A boundary on Paper 2 has ranged from 25 to 29 across six sessions — a spread of just 4 marks. This range sits meaningfully lower in percentage terms than the equivalent Biology Paper 2 boundary of 30 to 33, which tells you that Chemistry Paper 2 is genuinely harder on average. The questions test precise chemical knowledge including stoichiometric calculations, atomic structure, and organic chemistry reactions — none of which yield to guesswork. To score at A level on Paper 2, target 27 to 29 correct answers out of 40 (67%–72.5%). To secure a C, aim for 17 to 20 out of 40 (42.5%–50%).

Paper 4 — Theory Extended (80 marks)

Paper 4 is the backbone of the Chemistry IGCSE grade. At 80 marks it contributes twice the weight of either Paper 2 or Paper 6, and it is where the performance gap between A and A* students is widest. Chemistry Paper 4 is arguably the most challenging of the three theory papers in any IGCSE science — it combines written explanations, multi-step calculations, data interpretation, and extended descriptive answers across the full extended syllabus including stoichiometry, electrochemistry, rates of reaction, organic chemistry, and chemical analysis. You can practise Paper 4 questions by topic at Physics & Maths Tutor's IGCSE Chemistry Paper 4 past paper library.

The boundary trend on Paper 4 is the most striking story in this dataset. In June 2023 the A boundary was 48 out of 80 — that is 60%. By June 2025 it had risen to 57 out of 80 — 71.25%. That is a 9-mark increase in the A boundary over two years on the same paper format. The direction of travel is unambiguous: the Paper 4 A boundary in Chemistry has been climbing, and students preparing for June 2026 should plan accordingly. For students targeting A* overall, Paper 4 is not a paper to target the A boundary on — they need to be scoring comfortably above it, aiming for 57 to 62 out of 80 (71%–77.5%).

Paper 6 — Alternative to Practical (40 marks)

Paper 6 tests experimental skills without a live laboratory environment. Students must design experiments, interpret data from chemical investigations, draw and analyse graphs, and evaluate the limitations of experimental methods — all within 60 minutes and 40 marks. It is the paper most students underestimate and the one where targeted revision pays off most efficiently, because the skills it tests are highly structured and very teachable. All past Paper 6 papers and mark schemes are available at Physics & Maths Tutor's IGCSE Chemistry Paper 6 library.

The A boundary on Paper 6 has held between 29 and 31 out of 40 across every session in this period — a range of just 2 marks. This extraordinary stability makes Paper 6 the most predictable component to plan for. Students who work through past papers and understand the marking conventions for experimental design, variable identification, and conclusion writing can approach this paper with a clear target: 29 to 31 out of 40 (72.5%–77.5%) is what grade A looks like on Paper 6.

June vs November: where the Chemistry data tells a different story to Biology

In IGCSE Biology, the June versus November boundary comparison showed a relatively modest and consistent gap. Chemistry tells a different story. The gap between June and November A* boundaries in Chemistry over this period has ranged from 8 marks to 20 marks. In 2023 the November A* boundary was 149 versus June's 157 — an 8-mark gap. In 2024, November came in at 158 against June's 170 — a 12-mark gap. In 2025, the gap widened dramatically to 20 marks, with June at 173 and November at 153.

The June examination consistently demands more raw marks to reach A*, often significantly more. A student who sits Chemistry in November 2026 after a weak June sitting could be working toward a 155 to 163 total rather than a 171 to 175 total. That is a meaningful difference in practical terms — though the caveat applies equally here: choosing November purely for boundary reasons is not the same as being genuinely prepared to achieve A*. The decision on timing should be driven by readiness and school context, not boundary arithmetic alone.

What the grade boundaries mean for your Chemistry revision strategy

Targeting A*

To reach A* in Chemistry on Option CY, students need approximately 153 to 173 out of 200 depending on the session — with June 2026 likely requiring toward the upper end of that range. A working target that accounts for the upward June trend is 170 to 175 out of 200. Across the three papers, that translates to approximately 28–30 out of 40 on Paper 2 (70%–75%), 57–63 out of 80 on Paper 4 (71%–79%), and 30–32 out of 40 on Paper 6 (75%–80%). Paper 4 is where the A* is won or lost. The additional 8 to 12 marks above the A boundary that A* requires must come overwhelmingly from Paper 4.

Targeting A

Students aiming for grade A need approximately 126 to 146 out of 200, with June 2026 likely sitting toward 143 to 148. A working target per paper is 26–28 out of 40 on Paper 2 (65%–70%), 45–52 out of 80 on Paper 4 (56%–65%), and 28–30 out of 40 on Paper 6 (70%–75%).

Targeting C

Students securing a C need approximately 70 to 89 out of 200. With June sittings requiring the higher end of that range consistently, a safe planning target for June 2026 is 85 to 93. Per paper: 18–20 out of 40 on Paper 2 (45%–50%), 25–32 out of 80 on Paper 4 (31%–40%), and 17–20 out of 40 on Paper 6 (42.5%–50%).

If you are targeting IGCSE Chemistry revision with live, expert-led tuition, the IGCSE Chemistry course at chem-bio.info includes past paper walkthroughs, mark scheme technique sessions, and Paper 4 calculation practice aligned to the June 2026 syllabus.

Grade boundary prediction for IGCSE Chemistry June 2026

Six sessions of data and a clear upward trend in the June series provide a reasonable basis for predicting what June 2026 thresholds are likely to look like for Option CY. The methodology anchors on the mean of June 2024 and June 2025, adjusted conservatively upward for the Paper 4 trend and the structural consistency of the June cohort.

The Paper 4 prediction is the most consequential single number in this section. If the upward trend from 48 in June 2023 to 57 in June 2025 continues even at a moderated rate, students targeting A in June 2026 on Paper 4 should be planning to score 56 to 60 out of 80. These predictions are estimates grounded in historical data. Always refer to the official Cambridge International grade threshold tables after results are published in August 2026.

The Chemistry-specific challenge: why boundaries move and what students should do about it

Chemistry stands apart from Biology and Physics in one important way: the extended theory content in Paper 4 includes a higher proportion of multi-step problems — particularly stoichiometric calculations, equilibrium and rates questions, and organic synthesis pathways — where a single error in method can cascade into multiple lost marks. A Chemistry student who knows their content but makes systematic errors in mole calculations or forgets to balance equations will drop marks at a rate that Biology students rarely experience.

This is precisely why the Paper 4 A boundary has risen over this period. As more students arrive at the extended Chemistry exam with strong content knowledge — driven by improvements in online tutoring, resource availability, and past paper practice — Cambridge's awarding process naturally adjusts. Students should not be discouraged by a rising Paper 4 threshold; they should be motivated by it. It is evidence that strong preparation makes a measurable difference.

Frequently asked questions

Is the Chemistry A* boundary rising every year?

For the June series specifically, yes — the trend from June 2023 to June 2025 is upward, and notably so on Paper 4. The A* overall boundary moved from 157 in June 2023 to 170 in June 2024 to 173 in June 2025. The pattern for Chemistry is not a simple year-on-year rise — it is a consistent June premium over November, with the size of that premium varying.

Why does the Chemistry C boundary vary so much?

The C boundary in Chemistry has ranged from 70 in June 2023 to 89 in June 2025 — a 19-mark difference across just two years. It reflects how Cambridge calibrates the lower end of the grade distribution for a subject where cohort quality varies significantly between sessions and between schools. A student targeting a C in June 2026 should plan for a boundary in the range of 84 to 92.

How is Paper 6 different from Paper 5 in Chemistry?

Paper 5 is the live practical examination sat in school under laboratory conditions. Paper 6 is the Alternative to Practical, which tests the same experimental skills through a written paper without requiring laboratory access. Most international schools, including those across the GCC region, enter students for Paper 6 rather than Paper 5. The grade thresholds in this guide are for Option CY, which uses Paper 6. Students in schools entering Paper 5 should refer to the Option BY thresholds in the official threshold tables, where boundaries differ.

Can a strong Paper 2 offset a weak Paper 4 in Chemistry?

Not significantly, and less so in Chemistry than in Biology. Chemistry Paper 4 carries 80 raw marks — twice the weight of Paper 2. In Chemistry more than in any other IGCSE science, Paper 4 performance is the primary determinant of final grade. Paper 2 can move a student from one grade boundary to the next at the margin, but it cannot bridge a gap caused by a fundamentally weak Paper 4.

When will the June 2026 Chemistry grade boundaries be published?

Cambridge publishes grade threshold tables on the same day as examination results — typically mid-August. The exact date for August 2026 will be confirmed by Cambridge International in the months before results day.

Where can I find all the official Chemistry threshold tables?

All Cambridge IGCSE Chemistry (0620) grade threshold tables for past sessions are available at the Cambridge IGCSE grade threshold tables page.

Summary: six things every Chemistry student needs to know

• The A* boundary for IGCSE Chemistry (0620) Option CY has ranged from 149 to 173 across the past three years — a wider swing than any other IGCSE science.
• Paper 4 is the dominant component, carrying double the weight of Papers 2 and 6, and its A boundary has risen from 48 to 57 out of 80 across June sessions from 2023 to 2025.
• Paper 2 thresholds sit in a tight range of 25 to 29 out of 40 — lower in percentage terms than the equivalent Biology boundary, reflecting genuinely harder MCQs.
• Paper 6 thresholds are the most stable of the three components, with the A boundary holding between 29 and 31 out of 40 across all six sessions.
• June sessions consistently demand more marks than November sessions for A*, with the gap ranging from 8 to 20 marks across the three years covered here.
• For June 2026, a realistic A* target is 171 to 175 out of 200 — approximately 29 out of 40 on Paper 2, 57–60 out of 80 on Paper 4, and 31 out of 40 on Paper 6. Official 2026 boundaries will be published by Cambridge International in August 2026.

Analysis based on official Cambridge International IGCSE Chemistry (0620) grade threshold tables for June 2023, November 2023, June 2024, November 2024, June 2025, and November 2025. All data sourced directly from cambridgeinternational.org. For live IGCSE Chemistry tuition, revision classes, and study resources, visit chem-bio.info.