The formula
Classes you can miss now = attended ÷ target − conducted, rounded down, with the target as a decimal (75% is 0.75).
If the result is zero or less, you can't miss any class right now without dropping below your target.
A mid-semester example
You've attended 30 of 36 classes (83.3%).
- At 75%: 30 ÷ 0.75 − 36 = 4. You can miss 4 classes in a row and still be at 75% (30 of 40).
- At 80%: 30 ÷ 0.80 − 36 = 1.5, rounded down to 1. Missing a second class would leave you at 30 of 38, or 78.9%.
- At 85%: you're already below 85%. You need to attend the next 4 classes to reach 34 of 40.
Over a whole semester
If you know how many classes a subject will hold in the full semester, the most you can miss across the semester is total classes × (1 − target), rounded down:
| Classes in the semester | 75% target | 80% target | 85% target |
|---|---|---|---|
| 40 | 10 | 8 | 6 |
| 48 | 12 | 9 | 7 |
| 60 | 15 | 12 | 9 |
| 80 | 20 | 16 | 12 |
These are totals for the whole semester. Absences you've already taken count against them.
Attending earns you room
Every class you attend raises the number you can miss later. At 75%, each 3 classes attended earn 1 more absence. At 80%, it takes 4. At 85%, it takes roughly 6.
Before you skip
- Check the rule is per subject, not overall.
- Keep a margin. A surprise extra class, a lab counted twice or an illness can use it up.
- Your college's records decide, not a calculator.
Check your own numbers
The attendance calculator works out your percentage, the classes you can miss and the classes you need, for 75%, 80%, 85% or any target.