Short answer. Attendance percent = classes attended / classes held x 100. To reach a target t from below, attend n = (t x held - attended) / (1 - t) classes in a row, rounded up. To stay above it, you can skip (attended / t - held), rounded down.
How the attendance sum works
Attendance percent is the classes you attended divided by the classes held, times 100. If you attended 28 of 40 classes, you have 28 / 40 = 70%.
Every class you attend adds 1 to both numbers. Every class you miss adds 1 only to the classes held. This is why a low percent is slow to repair. You must attend more than the target share of the new classes.
Classes to attend in a row
Say you are below the target. Let a be classes attended, h be classes held and t be the target as a fraction. You need n more classes in a row so that (a + n) / (h + n) is at least t.
n = (t x h - a) / (1 - t), rounded up to a whole class.
The same idea shows why a high target is hard. At 75%, the bottom of the fraction is 0.25. At 90%, it is 0.10. A smaller number on the bottom makes n much larger.
Classes you can skip
Say you are at or above the target. You can miss s classes in a row if a / (h + s) is still at least t.
s = a / t - h, rounded down to a whole class.
The optional box
If you know how many classes are left in the term, type it in the last box. The tool then says how many of the remaining classes you must attend. It also says how many you can miss. If the number needed is more than the classes left, the target cannot be reached this term.
What this tool does not know
Rules differ by school. Some count each subject alone. Some count all subjects together. Some count lab hours apart from lectures. Some allow a medical or sports relaxation. Use the tool for planning, then read your handbook. The school record is the official one.
Worked example
Example. 28 attended out of 40 held. Target 75%.
Now: 28 / 40 = 70.0%. Attend 8 classes in a row. Check: (28 + 8) / (40 + 8) = 36 / 48 = 75.0%.
Now say you are at 36 of 40 (90%). You can skip 8 classes and stay at 75%. Check: 36 / (40 + 8) = 75.0%.
Questions
How do I find how many classes I can bunk?
Use s = a / t - h, rounded down. Here a is classes attended, h is classes held and t is the target as a fraction. For 36 of 40 at a 75% target, s = 36 / 0.75 - 40 = 8.
Do the missed classes have to be in a row?
The tool counts them as the next classes in a row. If you spread the misses out, the total is the same. Only the order changes, not the final percent.
Why is it slow to repair a low percent?
Each attended class adds 1 to both numbers, so the percent moves toward 100 only a little at a time. The higher the target, the more classes in a row you need.
What if my school counts attendance by subject?
Run the tool once for each subject, with that subject's numbers. The weakest subject sets the risk.
What if my school counts lectures and labs apart?
Run the tool once for lectures and once for labs. Many schools set a separate minimum for each.
Is the result official?
No. It is a plan. Your school attendance record is the official one, and some schools allow relaxation for illness or approved events. Ask your office.
Last checked by the StudyCount team.