The short answer is a candidate needs to earn 24 out of a possible 45 points. However, those 24 points must be earned while meeting the points stipulated below. The points are taken from Article 13 Award of the IB Diploma taken from the IB's Diploma Programme General Regulations

13.1 All assessment components for each of the six subjects and the additional Diploma requirements must be completed in order to qualify for the award of the IB Diploma.

13.2 The IB Diploma will be awarded to a candidate provided all the following requirements have been met.

• CAS requirements have been met.

• The candidate’s total points are 24 or more.

• There is no “N” awarded for theory of knowledge, the extended essay or for a contributing subject.

• There is no grade E awarded for theory of knowledge and/or the extended essay.

• There is no grade 1 awarded in a subject/level.

• There are no more than two grade 2s awarded (HL or SL).

• There are no more than three grade 3s or below awarded (HL or SL).

• The candidate has gained 12 points or more on HL subjects (for candidates who register for four HL subjects, the three highest grades count).

• The candidate has gained 9 points or more on SL subjects (candidates who register for two SL subjects must gain at least 5 points at SL).

• The candidate has not received a penalty for academic misconduct from the Final Award Committee.

From the General regulations: Diploma Programme May 2019 update

How is the IB Diploma scored?

• Each subject is graded 1–7, with 7 being the highest grade.

• These grades are also used as points (that is, 7 points for a grade 7, 6 points for a grade 6, and so on) in determining if the diploma can be awarded.

• TOK and the EE are graded A–E, with A being the highest grade. These two grades are then combined in the diploma points matrix to contribute between 0 and 3 points to the total.

• CAS is not assessed but must be completed in order to pass the diploma. See section “A2.2.2”.

• The overall maximum points from subject grades, TOK and the EE is therefore 45: ((6 × 7) + 3).

• The minimum threshold for the award of the diploma is 24 points. If a candidate scores less than 24 points, the diploma is not awarded.

How does the IB determine a 1-7 score for an individual subject?

Each subject is divided between an internal assessment, a possible external assessment and the exams, which constitute 1-3 Papers. Each of these components is provided with a percentage weight in order to combine them all together to create a single score. For example in Math Analysis and Approaches SL the internal assessment comprises 20% of the grade with Paper 1 and 2 each contributing 40% of the grade. These weightings change for Math Analysis and Approaches HL where the internal assessment is also 20%, but Paper 1 and 2 are 30% with Paper 3 contributing the final 20%.

Each component is scored independently, then multiplied by a number to make the score reflect its percentage weight. Then each component is added together to make a final number out of 100. Finally, the IB sets for each exam session an overall "markband" to determine what is a 7 versus what is a 6 and so on. For example in 2019, the last year exams were held, in Spanish ab initio a 7 was any score between 87 and 100. A 6 was any score between 73 and 86. These numbers may change slightly from year to year as the IB does statistical analysis after IB exams to ensure that the exams are of comparable rigor from year to year.