The IB total is made of two parts that are frequently treated as one. Six subject grades account for 42 of the 45 points, and the core accounts for the remaining 3.
The first part: six subjects
Each of the six subjects is graded from 1 to 7, where 7 is the highest. Six sevens give 42, which is the ceiling from subjects alone.
Higher Level and Standard Level subjects are scored on the same scale. A 7 at Standard Level is worth the same 7 points as one at Higher Level, a point covered separately under HL and SL.
The second part: the core bonus
The Extended Essay and Theory of Knowledge are graded on a letter scale and combined into a bonus worth between 0 and 3 points. Creativity, Activity, Service is not graded but has to be completed.
These 3 points are exactly the distance between 38 and 41, which is often the distance between two very different offers. They are also the part of the total that students prepare for last.
The diploma has its own conditions
Reaching 24 points is necessary but not sufficient. The diploma also requires the core to be completed and requires that certain failing conditions do not occur, which are covered under diploma requirements.
This is why a total on its own does not answer the question of whether a diploma was awarded.
What counts as a good score
The global average sits in the low thirties in most sessions. Selective universities commonly make offers between 36 and 42, often with specified Higher Level grades attached.
The Higher Level requirement matters as much as the total. An offer of 38 with 6, 6, 5 at Higher Level is not met by 38 built on strong Standard Level results.
When results are released
Results are published in July for the May session and in January for the November session. The predicted grades issued earlier by the school are what universities use to make conditional offers, which is why the predicted grade carries so much weight in the application.