Your timetable decides your attendance budget
You can work out roughly how many classes you can miss in each subject this semester before the semester even starts. All you need is your weekly timetable and the number of teaching weeks.
Step 1: count each subject's classes per week
Go through your timetable and count how many periods each subject has in a normal week. A typical result looks something like this:
| Subject | Periods per week |
|---|---|
| Subject A | 4 |
| Subject B | 4 |
| Subject C | 3 |
| Subject D | 3 |
| Subject E | 3 |
Step 2: estimate the semester total
Multiply by the number of teaching weeks. Then knock off a little for holidays and cancelled classes, because some always happen. If there are 15 teaching weeks and you expect to lose about a week to holidays, use 14:
| Periods per week | Semester total (14 weeks) | Max you can miss at 75% | At 80% |
|---|---|---|---|
| 3 | 42 | 10 | 8 |
| 4 | 56 | 14 | 11 |
| 5 | 70 | 17 | 14 |
The "max you can miss" is 25% of the total, rounded down (20% for an 80% cut-off). That's your skip budget for the whole semester, including days you're ill.
Step 3: find your riskiest subject
Two things make a subject risky:
- Fewer periods per week. A 3-a-week subject has a smaller budget than a 4-a-week one, so the same number of absences hits it harder.
- Bad time slots. Look at when each subject happens. If one subject has two or three first-period slots, it'll take the hit every time you're late. If one is always last on a Saturday, it'll take the hit every time you leave early.
A 3-a-week subject that's mostly in the first period is the one to watch.
Step 4: watch out for whole-day absences
When you miss a whole day, you miss every subject on it. Look at which days are heavy for your riskiest subject. If Monday has two periods of it, Mondays are expensive days to miss. If you have to take a day off, a day where your weakest subject doesn't appear costs you less.
Why it's an estimate
Extra classes, unexpected holidays and cancelled periods will move the real totals a bit. Recheck against your actual numbers every few weeks, using the calculator or an app that counts for you. But the estimate tells you early which subject needs care, which is the useful part.