Formula
Below target: x ≥ (target × held − 100 × attended) ÷ (100 − target)Above target: can miss ⌊attended × 100 ÷ target − held⌋
- x — consecutive classes to attend, rounded up
Solve (attended + x) ÷ (held + x) ≥ target for x, using whole classes.
Worked example
28 of 40 attended, need 75%
- Required attendance
- 75 %
- Classes held so far
- 40
- Classes attended so far
- 28
Classes to attend in a row
8
Current attendance: 70%
Attendance after those classes: 75%
How it works
Suppose you have attended 28 of 40 classes (70%) and need 75%. Each class you attend adds one to both the top and the bottom of the fraction, so 28 + x over 40 + x must reach 0.75, which needs x ≥ 8. After 8 classes you will be at 36 out of 48, exactly 75%.
If you are already above the target the question flips: how many classes can you skip while staying at or above it? That is the largest number of extra classes the total can grow by before your fraction drops to the target. Add the classes left in the term to check that the target is still reachable.
To see your current figure on its own use Attendance Percentage Calculator; marks percentages are on Marks Percentage Calculator.
Assumptions and limits
- Assumes you attend every one of the extra classes (or miss them, in the “can miss” case) with no partial attendance.