School absences can illustrate a district's ability to teach students. While no instructor wants students to miss class time, certain circumstances warrant a child staying home from school. The more a child is in school, however, the greater his opportunities for learning. An instructor or principal can easily calculate absence rates with a few simple math equations. However, instructors must keep dedicated and accurate attendance records to calculate truthful attendance and absence percentages.

Multiply the total number of students in a school or class by the total number of school days in a year. For example, if your school has 250 school days and 250 students, the perfect attendance number would be 62,500.

Add the number of each student's absences to get an absence total for the year.

Subtract the total number of absences from the perfect attendance number. The difference is your school's actual attendance number. For example, if your school of 250 students had 2,500 total absences, the actual attendance rate would be 60,000.

Divide the actual attendance rate by the perfect attendance rate.

Multiply this quotient by 100 to calculate the attendance rate in terms of a percentage. For example, 60,000 (the actual attendance number) divided by 62,500 (the perfect attendance number) equals .96. Multiply that by 100 to get a 96 per cent rate of attendance.

Subtract the rate of attendance percentage from 100 per cent to get the absence rate. For example, if the school has a 96 per cent attendance rate, the absence rate would be 4 per cent.