How to use the Attendance Calculator
- Enter classes attended and total classes held so far.
- Set the required attendance — 75% is common.
- Read your current percentage and the classes needed or the classes you can miss.
The formulas
Attendance % = Attended ÷ Total × 100
Classes needed = ⌈(Target × Total − Attended) ÷ (1 − Target)⌉
Classes you can miss = ⌊Attended ÷ Target − Total⌋
Target is written as a decimal: 75% = 0.75. ⌈ ⌉ rounds up and ⌊ ⌋ rounds down, because you can't attend part of a class.
Worked examples (75% target)
| Attended / held | Attendance | Result |
|---|---|---|
| 30 / 45 | 66.67% | Attend the next 15 classes → 45 / 60 = 75% |
| 40 / 50 | 80% | You can miss 3 → 40 / 53 = 75.47% |
| 75 / 100 | 75% | Exactly at the limit — missing the next class drops you below |
Before relying on the numbers
- Check whether your college counts attendance per subject or overall — many count it per subject.
- Some colleges count labs and tutorials separately or with different weight.
- Medical and other approved leave may be treated differently; ask your department.
Worked example
30 of 45 classes attended, 75% required
- Needed = (0.75 × 45 − 30) ÷ 0.25 = 15
Attend the next 15 classes in a row
Important notes
- The 'classes you can miss' figure assumes no other classes are held in between. As more classes happen, recalculate.
Frequently asked questions
How many classes can I miss and keep 75%?
Divide classes attended by 0.75 and subtract the total held so far; round down. With 40 of 50, that's 40 ÷ 0.75 − 50 = 3.3, so 3 classes.
How do I calculate attendance percentage?
Classes attended ÷ total classes × 100. 36 out of 48 is 75%.
Is 75% attendance compulsory?
Many universities and boards set 75% as the minimum to sit exams, but rules and exemptions vary. Check your institution's regulations.