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Attendance Calculator

See where your attendance stands, how many more classes you must attend to reach the requirement, and how many you can safely miss.

Runs entirely in your browser

How to use the Attendance Calculator

  1. 1Enter the total number of classes held so far and how many you attended.
  2. 2Set the minimum attendance your institution requires.
  3. 3Optionally enter how many classes are still to come this term.
  4. 4Read the verdict — either how many you can miss, or how many you must attend in a row.

How it works

Your current percentage is attended ÷ held. The interesting question is what happens next, and that depends on which side of the requirement you are on.

If you are above the line, the tool works out how many classes you could skip before your percentage drops below it — solving attended ÷ (held + skipped) ≥ required for the largest whole number of skips.

If you are below the line, it solves the mirror problem: how many consecutive classes you must attend for (attended + x) ÷ (held + x) to reach the requirement. There is a hard limit here that catches people out — if you have missed enough classes, no number of future attendances can rescue the percentage within the classes remaining. The tool checks this against your remaining classes and says so directly.

The formula

attendance % = (attended ÷ held) × 100 classes needed = ⌈(r × held − attended) ÷ (1 − r)⌉
attended
classes you were present for
held
classes conducted so far
r
required attendance as a decimal, e.g. 0.75 for 75%
⌈ ⌉
round up to the next whole class

The second formula only has a solution when the requirement is below 100%.

Worked example

38 attended out of 52 held, with a 75% requirement

  1. Current attendance is 38 ÷ 52 = 73.1%, which is below the line.
  2. Needed = (0.75 × 52 − 38) ÷ (1 − 0.75) = (39 − 38) ÷ 0.25 = 4.

Result: Attend the next 4 classes without missing one and you reach 75% exactly.

Frequently asked questions

How many classes can I miss and stay above 75%?
Enter your figures and the tool gives the exact number. As a rule of thumb, once you are at exactly 75% you can miss one class for every three you attend.
Why does it say the requirement cannot be met?
Because there are not enough classes left in the term. Once too many are missed, the arithmetic cannot recover within the remaining sessions — the tool tells you rather than showing an unreachable target.
Should I count cancelled classes?
No. Only count classes that were actually held, since those are what your institution's register records.

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