An Attendance Rate Calculator

An attendance rate is the days a student actually attended divided by the days they were enrolled for. The division is trivial; the two decisions around it are not, namely which days belong in the denominator and what the resulting percentage is being measured against.

Days attendedSessions the student was recorded present, counted over the same window as the days enrolled.Days enrolledSessions the student could have attended. Not calendar days, and not the class total if the student joined late.Minimum attendance rate(%)A policy figure such as 90. Used to work out how many absences the minimum still allows.

Attendance rate

95.56%

Days absent: 8
Absences the threshold allows: 18
Rate after one further absence: 95.00%

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

The formula this calculator uses

Attendance rate = Days attended / Days enrolled

present: Days attended — sessions the student was recorded present
possible: Days enrolled — sessions the student could have attended, not calendar days
threshold: Minimum attendance rate a policy requires, such as 90%
rate: Days attended divided by days enrolled, a fraction between 0 and 1

How to check the result by hand

1
Decide which days count as possible days
The denominator is the number of days the student was enrolled for. Exclude weekends and holidays the school did not meet, and exclude any part of the term before enrolment began or after it ended. If a student joined late, their 180 is smaller than the class figure, and the numerator must be counted over the identical window so that the two numbers describe the same period.
2
Count the days actually attended
The numerator is the number of sessions the student was recorded present, which is 172 in the worked record. Counting from the same start and end dates as the denominator is what keeps the division meaningful, and it is the step where a partial attendance register quietly corrupts the result. A register with a missing week usually understates the numerator rather than the denominator.
3
Divide attended by possible
172 / 180 = 0.9555555555555556. Keep the full decimal rather than rounding to 96% or even 95.6%, because the later comparisons are sensitive to small differences and rounding twice compounds the error. The fraction, not the displayed percentage, is the quantity the rest of the calculation should use.
4
Convert to a percentage and compare with the threshold
Multiply by 100 to get 95.56%, then compare it with the published minimum. At a 90% policy the student is above the line, but the comparison should use the unrounded fraction, 0.9555555555555556 against 0.90, rather than the two displayed percentages. Doing the comparison on rounded figures is how a genuine breach gets missed.
5
Work out how many absences remain before the limit
0.90 x 180 = 162 days must be attended, so 180 - 162 = 18 absences are tolerated. With 8 already on the record, ten absences remain. This step turns a rate into a budget, which is usually the number a student actually wants, and it is the point at which a bare percentage becomes useful for planning.

For worked examples, common mistakes and the limits of this formula, read the full How To Calculate An Attendance Rate page.