90% Attendance Calculator
Enter your classes held and attended to see whether you meet the 90% attendance requirement, how many classes you can still miss, or how many you must attend in a row to get back to 90%.
You are exactly at the limit — don’t miss the next class.
Step-by-step solution
- Current attendance = (45 ÷ 50) × 100 = 90%
- To stay at 90%: 45 ÷ (50 + y) ≥ 0.9
- y ≤ 45 ÷ 0.9 − 50 = 0 → you can miss 0 classes
90% attendance ready reckoner
Minimum classes you must attend, and the most you can miss, to be at exactly 90% after a given number of classes.
| Classes held | Must attend (min) | Can miss (max) |
|---|---|---|
| 10 | 9 | 1 |
| 20 | 18 | 2 |
| 30 | 27 | 3 |
| 40 | 36 | 4 |
| 50 | 45 | 5 |
| 60 | 54 | 6 |
| 80 | 72 | 8 |
| 100 | 90 | 10 |
| 120 | 108 | 12 |
| 150 | 135 | 15 |
| 200 | 180 | 20 |
The formula
Attendance % = attended ÷ held × 100. To stay at 90%, you can miss floor(attended ÷ 0.9 − held) more classes. If you are below 90%, attend ceil((0.9 × held − attended) ÷ 0.1) classes in a row.
Frequently asked questions
How many classes can I miss with a 90% attendance requirement?
Out of every 100 classes you can miss at most 10. For your own numbers, enter them in the calculator above — it accounts for classes already held.
How do I calculate if I have 90% attendance?
Divide classes attended by classes held and multiply by 100. If the result is 90 or more, you meet the requirement.
I am below 90%. How many classes must I attend?
Use (0.9 × held − attended) ÷ (1 − 0.9) and round up. For example, with 48 of 60 classes you need to attend the next 60 classes without a break.