For parents unfamiliar with the Diploma Programme, the key point is that an IB percentage does not translate directly into a familiar letter grade. IB grade boundaries convert a student's weighted assessment mark into a subject grade from 1-7, with cut-offs varying by subject, level, and examination session.
Six subject grades are added together, along with up to three points from Theory of Knowledge and the Extended Essay, to produce a Diploma score out of 45. This guide explains the calculation, why boundaries change, and how to interpret predicted and final results.
The IB scoring system
A full Diploma Programme student normally studies six subjects, commonly three at Higher Level and three at Standard Level.
| Diploma component | Grading | Maximum contribution |
|---|---|---|
| Six subjects | Each graded from 1-7 | 42 points |
| Theory of Knowledge and Extended Essay | Each graded A-E, then combined | 3 points |
| Creativity, Activity, Service | Compulsory completion requirement | 0 points |
| Maximum Diploma score | Subject and core points | 45 points |
For example, grades of 6, 6, 6, 5, 5, and 5 produce 33 subject points. If Theory of Knowledge and the Extended Essay add two core points, the final score is 35 out of 45.
An HL and SL grade contribute equally to the numerical total. A 6 adds six points at either level, although separate minimum conditions apply to the HL and SL subject groups.
IB grade boundaries explained
A grade boundary is the minimum overall mark needed for a particular subject grade. Assessment components are marked, adjusted according to their official weightings, and combined into an overall scaled mark. The boundaries for that course and session then convert the mark into a grade from 1-7.
Consider this hypothetical example:
| Scaled mark | Subject grade |
|---|---|
| 78-100 | 7 |
| 66-77 | 6 |
| 54-65 | 5 |
| 42-53 | 4 |
| 31-41 | 3 |
| 18-30 | 2 |
| 0-17 | 1 |
Here, 77 earns a 6 while 78 earns a 7. These figures are illustrative and are not boundaries for an actual IB course.
The official IB assessment explanation describes IB assessment as criterion-related. Students are judged against defined standards rather than ranked against classmates through a simple curve.
Why grade boundaries change
There is no universal rule that 70% equals a 7. Subjects have different assessment demands, HL and SL courses differ, and examination difficulty can vary between sessions.
The IB's assessment guidance explains that grade awarding considers candidate work, grade descriptors, examiner judgment, statistical evidence, and information about the examination. This helps maintain comparable standards when one paper proves more demanding than another.
Boundaries are therefore not simply chosen to make a predetermined percentage of candidates pass. The official Diploma Programme grade descriptors describe the broad qualities associated with each achievement level. RevisionDojo's IB grade boundaries database provides useful historical context, but previous cut-offs cannot guarantee future boundaries.
How coursework and examinations combine
A final result may include examinations, an Internal Assessment, oral work, performances, portfolios, or other course-specific components. Each has an official weighting, so parents should not calculate a simple average of paper percentages.
For example, a component weighted at 20% contributes one fifth of the scaled final mark, regardless of its raw mark total. Teacher-marked work may also be externally moderated. Moderation can change marks when the school's use of assessment criteria differs from the IB standard, which helps explain why school estimates and final results sometimes differ.
TOK, the Extended Essay, and CAS
Theory of Knowledge (TOK) and the Extended Essay (EE) are graded from A-E. Their grades are combined through the official core points matrix to award 0-3 points.
A B in TOK and C in the EE produce two core points. A C and D produce zero points but do not, by themselves, prevent the Diploma from being awarded. An E in either component is a failing condition.
Creativity, Activity, Service (CAS) adds no numerical points, but completing it is compulsory. It cannot be ignored simply because it does not increase the score.
Why 24 points do not guarantee the Diploma
The minimum total is 24 points, but that is only one award condition. Under the current IB Diploma passing criteria, a candidate must also:
- complete CAS;
- receive grades in all six subjects, TOK, and the EE;
- avoid an E in TOK or the EE;
- avoid a grade 1 in any subject;
- receive no more than two grades of 2;
- receive no more than three grades of 3 or below;
- obtain at least 12 points across three counting HL subjects;
- obtain at least 9 points across three SL subjects, or 5 when taking two SL subjects; and
- avoid a disqualifying academic misconduct penalty.
A student can therefore reach 24 points without receiving the Diploma. Equally, every subject does not need to be graded 4 or above if the entire profile satisfies the rules. University offers remain separate and may require a higher total or a specific HL grade.
Interpreting predicted and final grades
A predicted grade is a teacher's professional estimate based on evidence such as mock examinations, timed work, coursework, and classroom assessments. It is not an official result and cannot use future boundaries that have not yet been established.
Parents should ask whether the prediction applies the correct component weightings, includes all available assessments, and places the student securely within a grade range or close to a boundary. RevisionDojo's IB Grade Calculator can estimate outcomes from representative practice marks, but it remains a planning tool rather than a guaranteed prediction.
The IB's assessment FAQ explains that detailed results information can include the scaled total, grade boundaries, and marks needed for an increase. Access is managed through the school's IB coordinator.
If a result is close to the next boundary, families should not assume a re-mark will raise it. Ask about eligible components, fees, deadlines, and the possibility of a decrease. RevisionDojo's guide to IB Enquiries Upon Results explains this decision, while its parents' results day guide covers university conditions and next steps.
Common misunderstandings
- A 7 means at least 70%. False. The cut-off depends on the course and session.
- A 4 is always a pass. False. Diploma award conditions consider the full grade profile.
- Twenty-four points guarantee the Diploma. False. All additional conditions must be met.
- CAS is optional because it adds no points. False. Completion is compulsory.
- Boundaries are a class curve. False. IB assessment is criterion-related, although statistical evidence supports comparability.
Conclusion
IB grade boundaries convert weighted marks into subject grades from 1-7. Six subjects contribute up to 42 points, while TOK and the EE can add three, producing the maximum score of 45.
Parents should consider the correct subject, level, session, weightings, and distance from a boundary rather than interpreting the mark as a conventional percentage. RevisionDojo's Grade Boundaries, Grade Calculator, Questionbank, and Mock Exams can support informed monitoring and focused practice.
Sources and referenced URLs
- IB assessment overview
- IB student assessment guidance
- Official IB grade descriptors
- IB Diploma passing criteria
- IB assessment and results FAQ
- RevisionDojo IB Grade Boundaries
- RevisionDojo IB Grade Calculator
- RevisionDojo Enquiries Upon Results guide
- RevisionDojo parents' results day guide
- RevisionDojo IB Questionbank
