Attendance calculator: how many classes can you miss?
Enter how many classes you've attended and how many have been held. The calculator shows your percentage and what it means for the next few classes. Nothing you type leaves your phone.
What the numbers mean
Attended is the number of classes you were marked present for. Held is the number of classes that actually happened, including the ones you missed. Classes that were cancelled, or periods where no teacher came, usually don't count as held, so leave them out of both numbers.
If you're above your target, the calculator tells you how many classes you could miss in a row from now and still be at or above it. If you're below it, it tells you how many classes in a row you'd need to attend to climb back.
The formulas behind it
Your percentage is simply:
Attendance % = attended ÷ held × 100
To find how many more classes you can miss while staying at 75%, the calculator finds the biggest number y where attended ÷ (held + y) is still at least 0.75:
Classes you can miss = attended ÷ 0.75 − held (rounded down)
To find how many you need to attend to get back to 75%, it finds the smallest x where (attended + x) ÷ (held + x) reaches 0.75:
Classes needed = (0.75 × held − attended) ÷ 0.25 (rounded up)
For any other target, swap 0.75 for your target as a decimal, and 0.25 for one minus it. For 80%, that's 0.80 and 0.20.
Do this per subject, not just overall
Many colleges check attendance subject by subject, so a healthy overall number can hide one subject that's below the line. Run the calculator separately for each subject using that subject's own attended and held counts. There's more on this in subject-wise vs overall attendance.
This is a calculator, not your official record. The college register decides your attendance, and every college sets its own rules for the cut-off, medical leave and exceptions.