IB grade boundaries are the minimum marks needed for each grade from 1 to 7 in a given IB subject. They are one of the most misunderstood parts of the IB, partly because they move from one exam session to the next and partly because they work differently from the fixed percentage scales used in many other systems. This guide explains what grade boundaries are, why they vary, and how to use them sensibly without treating them as a prediction of your own result.
What is an IB grade boundary?
For each IB subject and level (Higher or Standard Level), the IB sets a grade boundary: the total mark a student needs to reach a particular grade. A grade 7 boundary means anyone scoring at or above that mark receives a 7. Boundaries are published for each subject, each level and each exam session (May and November).
Because the boundary is a mark threshold rather than a fixed percentage, two students with the same percentage can receive different grades if the total marks available differ between papers or components. The grade you receive depends on where your total mark sits relative to the boundaries set for that subject and session.
Why boundaries differ by subject, level and session
Grade boundaries are not universal. A boundary that produces a grade 7 in Mathematics AA HL will not be the same as the boundary for Chemistry HL or Economics HL, because each subject has a different paper structure, total marks and difficulty profile. Higher Level and Standard Level boundaries differ because the papers themselves differ.
Boundaries also move between the May and November sessions and from year to year. If a paper turns out to be harder than intended, the boundaries may move down so that the same standard of performance is still rewarded with the same grade. If a paper is easier, boundaries may move up. This is what keeps the IB grade standard stable over time, even though the raw marks change.
Why a raw mark is not a fixed percentage
Many students assume that a grade 7 means "around 80%" or that a grade 6 means "around 70%". This is misleading. The IB combines marks across multiple components, for example external exam papers and the Internal Assessment, and applies boundaries to the combined total, not to a simple percentage. The weighting of each component, the number of marks available, and the difficulty of that particular paper all affect where the boundary lands.
This is why comparing your practice paper percentage directly to a previous session's boundary can be inaccurate: your percentage is on one paper, while the published boundary applies to the combined total across all components for that session.
How boundaries are set
After each exam session, the IB reviews how students performed and sets grade boundaries that maintain consistent standards. The process takes account of statistical evidence and the professional judgement of examiners. Boundaries are then published by the IB so that schools and students can see them. If you want to look at boundaries for a past session, use the official IB grade boundary documents published after results, rather than relying on third-party tables that may be out of date or incorrect.
How to use grade boundaries in revision
Used carefully, past boundaries can help you set realistic targets. Once boundaries for a recent session are published, you can see roughly how many marks were needed for each grade in your subject and level. This gives you a sense of the standard required, which is more useful than a vague aim to "do well".
- Look at the combined total, not one paper. Boundaries apply to the overall subject grade, so track your performance across all components, including your Internal Assessment.
- Use boundaries as a guide to standard, not a prediction. They tell you what past cohorts needed, not what you will get. Your own result depends on your performance on the day.
- Focus on where you lose marks. If you know roughly how many marks separate grades, you can prioritise the topics and question types where you are losing the most.
- Re-check official sources each session. Boundaries move, so do not plan around a single older number.
What grade boundaries do not tell you
Boundaries tell you the threshold for each grade in a past session. They do not tell you what the boundary will be in your session, what grade you are on track for, or how the paper you sit will be weighted. They also do not tell you how to improve, because that comes from understanding the content and the mark scheme. Treating a past boundary as a guarantee is a common mistake; it is better to treat it as context for your revision.
Internal Assessment and the overall grade
The Internal Assessment (IA) contributes a set percentage of your final subject grade, and the exact weighting varies by subject. Because the IA is completed before the final exams and is partly within your control, a strong IA can support your overall mark. When you look at grade boundaries, remember that the boundary applies to the combined total, so your IA marks count towards the threshold just as exam marks do.
A sensible approach
Grade boundaries are useful context, not a target to game. The most reliable way to reach the grade you want is to understand the subject, practise against the mark scheme, and keep checking your performance across all components. If you would like support with a specific IB subject, HK Study Hub offers 1-to-1 tutoring across the IB, including IB Maths and IB Physics. You can also browse more IB resources.
Sources & Further Reading
- IB Diploma Programme assessment and exams— Official IB assessment information and grade boundaries