Attendance Calculator
Check your attendance and see how many classes you can miss, or must attend, to stay above 75%.
How it works
- Enter how many classes you have attended and how many were held.
- Set the attendance you need, usually 75%.
- See how many classes you can still miss, or how many in a row you must attend.
Frequently asked questions
How is attendance percentage calculated?
Classes attended divided by classes held, times 100. Attending 36 of 40 lectures is 90% attendance.
How many classes can I miss and stay at 75%?
Divide the classes you have attended by 0.75 and subtract the classes held so far. With 36 of 40 attended, 36 ÷ 0.75 − 40 = 8, so you can miss the next 8 classes.
How many classes do I need to get back to 75%?
Every class you attend from now on counts as both held and attended. The calculator finds the smallest run of classes that lifts you to the target: from 20 of 30, you need 10 in a row.
Do labs and tutorials count separately?
Many colleges track theory, labs and tutorials separately, each with its own 75% rule. Run the numbers for each one so a single subject does not hold you back.
The maths behind the answer
If you have attended a classes out of h and need a share r (0.75 for 75%):
- You can miss ⌊a ÷ r − h⌋ more classes, because every class you miss adds to the total held but not to the classes attended.
- If you are below the target, you need ⌈(r × h − a) ÷ (1 − r)⌉ classes in a row, because each class you attend adds one to both numbers.
Example: at 20 out of 30 (66.7%), reaching 75% takes (0.75 × 30 − 20) ÷ 0.25 = 10 classes. After them you are at 30 out of 40, exactly 75%.
Plan ahead, not at the last minute
Shortage rules are usually applied per subject, and medical or duty leave may be counted differently. Check your college's rules, and keep a small buffer rather than sitting exactly on the limit.