IB Diploma Grade Boundaries Explained

IB Diploma Grade Boundaries Explained (USA): How Scores Convert to 1–7

Raw marks are the points a student earns on an IB exam paper, internal assessment, oral, essay, project, or other assessed component. Scaled marks are adjusted marks used when components have different weights. Grade boundaries are the mark ranges that convert a student’s total performance into an IB subject grade from 1 to 7, with 7 as the highest grade. For US parents and students, the most important point is simple: IB grade boundaries are not fixed percentages; they vary by subject, level, component, and exam session.

This IB Diploma grade boundaries explained (USA) guide walks through how a paper score becomes a final 1–7 subject grade. It also explains why two students in different subjects, or in different exam sessions, may need different marks to earn the same IB grade.

How do IB grade boundaries work?

IB grade boundaries work by dividing final marks into ranges for grades 1 through 7 after assessments have been marked, moderated, weighted, and reviewed. The IB explains that assessment components have marks and weights, then total scores are placed into the 1–7 marking scheme; those ranges are the grade boundaries. The IB also says boundaries are set mainly by reviewing candidate work against grade descriptors, which describe the standard expected for each grade. (ibo.org)

That means an IB 6 is not simply “90% or above,” and an IB 4 is not the same as a US classroom “passing grade.” A 4 in one subject might require a different final mark than a 4 in another subject because the exams, rubrics, and candidate performance are different.

The 1–7 scale in plain English

Each IB Diploma Programme subject receives a grade from 1 to 7. A 7 represents the strongest level of achievement, while 1 represents the lowest. These subject grades are added together across six subjects, and students can also earn up to three additional core points from Theory of Knowledge and the Extended Essay. The maximum full diploma score is 45 points. (ibo.org)

For US families, it helps to separate three ideas:

• IB subject grade: the 1–7 result in one course, such as Biology HL or English A SL.

• Total diploma score: the sum of six subject grades plus possible core points.

• College credit or placement: a decision made by each US college or university, not by the IB.

A student may care about all three, but grade boundaries only explain how assessment marks become the IB subject grade.

How raw marks convert to scores from 1 to 7

The conversion from raw marks to a 1–7 grade happens in stages. The exact numbers differ by subject and session, but the process is broadly consistent.

1. The student completes assessment components. A subject may include exam papers, an internal assessment, oral work, essays, portfolios, or practical tasks, depending on the course.

2. Each component receives raw marks. For example, an exam paper might be marked out of 50, while an internal assessment might be marked out of 24.

3. Component marks are checked and, where needed, moderated. Externally marked work is marked by IB examiners. Internal assessments are marked by teachers and then moderated by the IB to support a consistent global standard.

4. Marks are weighted. If Paper 1 counts for 30%, Paper 2 counts for 40%, and the internal assessment counts for 30%, the raw marks are converted into weighted contributions.

5. Weighted marks are combined. The result is a final total or scaled total mark for the subject.

6. Grade boundaries are applied. The final mark is compared with that session’s boundaries for that subject and level.

7. The student receives a 1–7 grade. If the final mark falls within the 6 range, the student earns a 6; if it reaches the 7 range, the student earns a 7.

A simplified example might look like this:

• Paper 1: raw mark converted into its weighted share

• Paper 2: raw mark converted into its weighted share

• Internal assessment: moderated mark converted into its weighted share

• Final total: compared with that subject’s grade boundaries

• Final result: reported as a grade from 1 to 7

The key is that the raw percentage on one paper is not the final grade by itself. The final 1–7 result comes after all required components are combined according to the course assessment model.

Why boundaries vary by subject and session

Grade boundaries vary because IB assessments are not identical across subjects or sessions. A May Chemistry HL paper, a November History SL paper, and a Mathematics AA HL paper all test different skills and have different mark schemes. Even within the same subject, a later session may have different papers, different candidate performance, and different boundary decisions.

The IB has two main exam sessions each year, May and November, and results are released on different schedules for those sessions. (ibo.org) Because boundaries are determined for each assessment session, families should avoid relying on old boundary charts as guarantees. Past boundaries can be useful for practice and perspective, but they are not promises.

This is also why “IB Diploma grade boundaries explained (USA)” searches can be confusing. Many online charts show past boundaries, but a US student’s actual result depends on the official boundaries for that exact subject, level, and session.

Key Takeaways

• IB grades run from 1 to 7 for each subject, with 7 as the highest.

• Grade boundaries are mark ranges, not fixed percentages.

• Boundaries vary by subject, level, component, and exam session.

• Raw marks are combined and weighted before the final grade is assigned.

• Internal assessments may be moderated, so the teacher’s original mark may not always be the final mark used.

• The full diploma requires more than a certain total score; students must also meet specific passing conditions.

What parents and students should do with boundary information

Use boundaries as a planning tool, not a prediction machine. A student who is close to the next grade should review mark schemes, examiner comments when available, and teacher feedback to see where marks are being lost. The most useful question is not “What percentage do I need?” but “Which skills does the next grade require, and where can I gain marks reliably?”

Students should also ask their DP coordinator or teacher how a course is weighted. Knowing that an internal assessment counts heavily, for example, can help a student manage time before exams. After results are released, candidates may have access to details such as scaled total mark, lower and upper grade boundary, and marks needed for a grade increase, depending on what the school’s IB coordinator provides. (ibo.org)

FAQ

Do IB grade boundaries change each session?

Yes. Grade boundaries can change each session because they are linked to the specific assessments, candidate work, and grade-award process for that subject and level. Do not assume last year’s boundary will apply this year.

Are May and November session boundaries different?

They can be. May and November are separate examination sessions, so a subject’s boundaries may differ between them. The subject content may be similar, but the actual papers, cohort, and awarding evidence can lead to different boundaries.

Are HL and SL pass thresholds the same?

For individual IB courses, the IB does not assign a simple “passing score”; students receive a 1–7 course grade. For the full diploma, students need at least 24 total points and must meet additional conditions, including at least 12 points across HL subjects and at least 9 points across SL subjects, with special rules for students taking four HLs or only two SLs. (ibo.org)

How does IA moderation work?

Internal assessment, often called IA, is usually marked first by the teacher. The IB then moderates samples to check whether the school’s marking aligns with the global standard. If marks are judged too generous or too strict, adjustments may be applied so students are assessed consistently.

Can a student challenge a grade near a boundary?

A school can discuss an enquiry upon results with the student and family. The IB notes that re-mark requests must go through the school’s coordinator, may involve a fee, and can result in a grade going up or down. (ibo.org)

Final thought

IB grade boundaries are best understood as a fairness tool. They help turn different papers, projects, and assessment components into a consistent 1–7 grade, while recognizing that every subject and session is different. For US students, the smartest approach is to focus less on fixed percentages and more on the skills, evidence, and mark criteria that move work into the next grade band.