Cambridge IGCSE Grade Boundaries Explained: What Score Do You Need for A* to C in 2026?
Information current as of Term 2, 2026.
One of the most common questions from IGCSE students and parents in Kenya is: "What percentage do I need to get an A*?" The honest answer is more complicated than most people realise: and understanding it properly can genuinely change how you plan revision. This guide explains exactly how Cambridge IGCSE grade boundaries work, walks through a worked example of converting a target grade into a mark target, and sets out typical boundary ranges so you can plan with real numbers rather than guesswork.
- Grade boundaries are set after each examination session based on how the whole global cohort performed: they are never fixed in advance, regardless of what any textbook or tutor claims.
- A* on Extended papers has historically required roughly 85–93%+, but this genuinely moves session to session depending on paper difficulty.
- Core papers cap out at grade C: there is no route to A or A* on the Core tier, no matter how well a candidate scores.
- Build a "safe buffer" into your target score (aim a few percentage points above the historical boundary), since boundaries can shift after a particular session.
- Official, confirmed boundaries are published free on cambridgeinternational.org after each results release: always check there, not a forwarded WhatsApp message, for the real figures.
What Are Grade Boundaries?
Grade boundaries are the minimum raw mark a candidate must achieve in each examination paper, or combination of papers, to be awarded a particular grade. They are set by Cambridge International Examinations (CIE) after each examination session, once all scripts have been marked and statistical data on the whole cohort's performance is available.
This is the single most important thing to understand: grade boundaries are not fixed in advance. Cambridge does not pre-set "90% equals A*" as a permanent rule across all subjects and sessions. The boundaries move up or down depending on how the specific paper performed across all candidates worldwide who sat it that session.
How Cambridge Sets Grade Boundaries
After each examination, Cambridge Chief Examiners review a statistical sample of marked scripts and a selection of papers from candidates across different ability levels. They assess:
- Whether the paper was harder or easier than intended, based on overall mark distribution compared with previous sessions.
- Where the natural performance clusters fall in the mark distribution: grade boundaries are typically set at points where performance naturally separates into bands, not at arbitrary round numbers.
- Historical grade boundary data for that specific paper component, to maintain reasonable year-on-year comparability for universities and employers.
The outcome is a set of grade thresholds: the minimum mark for each grade from A* down to G: that reflect the real performance of that particular examination in that particular session. A paper that was unexpectedly difficult will have lower boundaries; an easier paper will have higher ones. This is precisely why "what mark gives an A*" cannot be answered with one permanent number.
Worked Example: Converting a Target Grade Into a Mark Target
Suppose a student is sitting IGCSE Mathematics 0580 Paper 4 (Extended), worth 130 marks, weighted at 65% of the overall subject grade, and the historical A boundary on this paper has typically sat around 75% of available marks.
Step 1: Calculate 75% of 130 marks: 130 × 0.75 = 97.5 marks, so the realistic historical target is approximately 98 marks.
Step 2: Add a safety buffer of 5 percentage points to account for boundary movement, since boundaries can shift session to session: 130 × 0.80 = 104 marks as the safer working target.
Step 3: Break this down by topic using past paper mark allocations. If Algebra and Number questions typically carry 45 of the 130 marks combined, aim to drop no more than 5–8 marks total across those two topic areas in practice papers, since they form the largest scoring block.
This three-step method: convert percentage to raw marks, add a buffer, then map the target onto specific topic areas using past paper mark schemes: turns a vague goal like "I want an A" into a concrete, trackable revision target.
Typical Grade Boundary Ranges: What to Expect
While boundaries vary by subject and session, the following ranges are broadly representative of what Cambridge IGCSE Extended papers have historically required. Use these as planning benchmarks, not as guarantees for any specific upcoming session:
| Grade | Typical % Range (Extended) | What It Signals |
|---|---|---|
| A* | 85% – 93%+ | Outstanding: typically the top 5–10% of candidates |
| A | 75% – 84% | Strong performance with few significant gaps |
| B | 63% – 74% | Good understanding with some inconsistency |
| C | 50% – 62% | Minimum acceptable for most university programmes |
| D | 40% – 49% | Below standard; university entry unlikely without alternative qualifications |
| E | 30% – 39% | Lowest grade reported on Extended; significant content gaps |
These are indicative ranges based on historical patterns. Actual 2026 boundaries will differ by subject and session. For confirmed figures, always check the Cambridge International website after results are published.
Grade Boundaries for Core vs Extended
Core papers have their own separate boundary tables. On Core, the maximum achievable grade is C: there is no A or A* route on Core, regardless of score. Typical Core boundaries are:
| Grade | Typical % Range (Core) |
|---|---|
| C (maximum on Core) | 65% – 70% |
| D | 50% – 60% |
| E | 40% – 50% |
| F | 28% – 38% |
| G | 18% – 27% |
If your child is on Core and targeting a grade C for university access, they need to be scoring consistently well above 65% in practice papers: to allow a buffer for exam-day conditions and any unexpected boundary movement.
Where to Find Official Grade Boundaries
Cambridge publishes official grade threshold tables (grade boundaries) for every examination series free of charge at cambridgeinternational.org, available after each results release: typically August for the May/June session, and January for the October/November session. You can search by syllabus code (e.g. 0580 for Mathematics, 0610 for Biology, 0620 for Chemistry, 0625 for Physics), by paper component, and by examination session.
How to Use Grade Boundaries in Your Revision Planning
- Set a target score backwards from the grade, not forwards from a guess. If you are aiming for an A in Mathematics, work out the historical raw mark equivalent for that paper using the method shown in the worked example above.
- Identify where marks are concentrated. Look at past papers and mark schemes: some topics carry far more marks than others. In Mathematics, Algebra and Number together often make up 35–40% of a paper; in Physics, Electricity and Mechanics typically dominate. Prioritise revision time accordingly.
- Build a safe buffer. Never aim exactly at the historical boundary. Boundaries can move 1–5 marks in either direction between sessions. If targeting A*, practise to a level that comfortably clears 90%+, not exactly 85%.
- Track practice scores against historical boundaries over time, not just once. If timed past paper scores are consistently sitting at 78–82%, that candidate is in a genuinely strong A position. If scores sit around 60–62%, a more structured intervention is needed well before the real exam.
Case Study: Using Boundaries to Plan a Revision Sprint
Take Wanjiru, a Grade 11 (Year 11) student in Nairobi sitting IGCSE Chemistry 0620 in the October/November session. Her first full past paper attempt, done eight weeks before the exam under timed conditions, scored 68%: solidly grade B territory based on historical boundaries, but short of her target grade A (typically 75%+). Rather than revising everything equally, she used her marked paper to identify that she lost the most marks in Organic Chemistry and quantitative Stoichiometry questions specifically, while scoring close to full marks on Atomic Structure and the Periodic Table. She spent four of her eight remaining weeks doing focused topical practice only on those two weak areas, using question banks rather than full papers, then sat a second full past paper. Her score rose to 79%: comfortably inside the historical A band with some buffer. The lesson: grade boundary awareness is only useful when combined with honest, topic-level error analysis, not generic revision.
Common Mistakes Students Make With Grade Boundaries
- Treating a single year's boundary as a permanent rule. Boundaries genuinely shift session to session: a boundary from three years ago is a guide, not a guarantee.
- Aiming exactly at the boundary instead of comfortably above it. This leaves zero margin for a harder-than-expected paper or an off day.
- Confusing Core and Extended boundary tables. They are entirely separate; checking the wrong one gives a meaningless comparison.
- Ignoring paper weighting. In subjects with multiple components (e.g. Mathematics Papers 2 and 4, weighted 35%/65%), a strong score on the lower-weighted paper cannot fully compensate for a weak score on the higher-weighted one.
- Not checking the specific session's boundaries after results day. Many students never actually look up the real boundary that applied to their sitting, missing a chance to understand exactly how close they were to the next grade up.
- Grade boundary (grade threshold): the minimum raw mark needed to achieve a specific grade, set after marking is complete for that session.
- Raw mark: the actual number of marks scored on a paper, before any conversion to a grade.
- Weighting: the percentage a particular paper contributes to the overall subject grade, e.g. Paper 4 at 65%.
- Ungraded (U): the outcome when a candidate's mark falls below the lowest grade boundary (G on Extended, or the equivalent on Core).
Frequently Asked Questions
- Do grade boundaries differ between the May/June and October/November sessions?
- Yes. Each examination series has its own boundaries because each paper is different. The October/November session in Kenya can have noticeably different boundaries from the May/June session for the same subject. Always check the boundaries for the specific session sat, not a different one.
- Can Cambridge lower boundaries significantly after a hard paper?
- Yes. After particularly challenging papers, Cambridge has lowered A* boundaries to below 80% in some subjects and sessions. This is intentional: it ensures a harder-than-usual paper does not unfairly penalise well-prepared students simply because the questions were more demanding that session.
- Is it possible to get a U (Ungraded) on IGCSE?
- Yes. If a candidate's marks fall below the lowest grade boundary (G on Extended, or the equivalent threshold on Core), they receive a U. This is rare for students who genuinely sat and attempted the paper in good faith.
- Why did my mock exam grade boundaries look different from the real Cambridge ones?
- Schools often set their own internal mock boundaries based on estimates or the previous year's published figures, since the real session-specific boundaries do not exist until after that exact paper has been sat and marked globally. Treat mock boundaries as a rough guide only.
- Do all four sciences and Mathematics use the same boundary pattern?
- No: each subject and even each paper component within a subject has its own independently set boundaries. A* in Physics 0625 and A* in Biology 0610 can require different percentage scores in the same session. See our companion guide on IGCSE Chemistry vs Biology vs Physics for how the three sciences compare in difficulty and demand.
- How many marks' difference is there typically between adjacent grades, like B and A?
- This varies by subject and paper length, but on a 130-mark paper it is common to see roughly 12–18 marks separating adjacent grade boundaries in the A*-to-C range. This is why focused topic revision: closing a 10–15 mark gap: can realistically move a candidate up a full grade.
- Where can I find official past grade boundary data to practise against?
- Cambridge publishes historical grade threshold documents on cambridgeinternational.org for several recent years per subject. Combine these with timed past paper practice: our guide on using past papers and mark schemes properly explains exactly how to structure that practice.
- Does taking the Extended paper instead of Core always lead to a better outcome?
- Not automatically. Extended unlocks A* to E, but a candidate who is realistically a strong C-grade performer may score more securely, and with less exam-day stress, sitting Core and achieving a confident C than risking a D or E on a harder Extended paper. This decision should be made with the subject teacher based on consistent classroom performance, not ambition alone.
Bottom Line for Students and Parents
Grade boundaries are a moving target by design: they exist to make Cambridge IGCSE grades fair and comparable across very different papers and years, not to give students a fixed percentage to memorise. The practical takeaway is simple: use historical ranges to set an ambitious but realistic mark target, build in a buffer, and direct revision time at the topics carrying the most marks rather than spreading effort evenly. For structured help building exactly this kind of topic-level revision plan, explore the IGCSE past papers and marking schemes catalogue, or get instant subject-specific explanations any time with Somo, our AI tutor: KSH 300 per month, 30 questions a day.
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