Formula: attended ÷ possible x 100
How-to guide
How to calculate school attendance percentage
School attendance percentage is worked out by dividing attended time by possible time, then multiplying by 100.
If your school gives you sessions instead of days, use sessions for the most accurate estimate.
Last reviewed: 12 July 2026 by Site editor and maintainer (Paul R).
Reviewed for general accuracy. Always check your school, local authority or official guidance for decisions.
Days and sessions both work, but sessions are often more precise.
The result is only as accurate as the totals you start with.
The basic formula
The simplest version is: attendance percentage = attended days divided by possible days, multiplied by 100.
If your school gives you session totals instead, use attended sessions divided by possible sessions, multiplied by 100.
Days versus sessions
Using days is often easier when you only know how many full days were missed.
Using sessions is usually better when there have been partial absences, because one missed morning or afternoon still changes the attendance total.
Common mistakes
A common mistake is dividing missed days by possible days and treating that as the attendance percentage. That gives the absence percentage, not the attendance percentage.
Another common mistake is forgetting that one full school day is usually two sessions.
- Use attended time, not missed time, in the top part of the formula
- Make sure the possible total matches the same unit: days with days, sessions with sessions
- Check whether the school figure is based on a term total or a full-year total
Official guidance
Check the official guidance alongside this guide
This page is an independent explainer. For formal questions about attendance rules, school decisions or local processes, compare it with your school's attendance policy, local authority guidance and the official resources collected on this site.
Worked examples
See the attendance maths in context
Day-based example
180 attended days / 190 possible days x 100 = about 94.7%
This is a simple way to estimate full-year attendance if you know total days attended or missed.
Session-based example
361 attended sessions / 380 possible sessions x 100 = 95%
This is often the better method if the school talks about sessions or if there have been partial absences.
Guide FAQs
Common questions about this attendance topic
These answers are general information only and are not a substitute for school records or official guidance.
What is the formula for school attendance percentage?
Attendance percentage = attended time divided by possible time, multiplied by 100.
Should I use days or sessions?
Use whichever figures you have, but sessions are often more precise because many schools record attendance by morning and afternoon session.
Why does my result not exactly match the school figure?
The school may be using session totals, different possible totals so far or recorded codes that change how attendance is counted.
Can this calculator replace the school register?
No. It gives estimates only and should not be treated as a substitute for official school records.