Methodology

How we calculate attendance

This page explains the calculator methodology in plain English, including the formula, days versus sessions, full-year assumptions, worked examples and the reasons a school record may look different.

Use the calculator Official resources

Estimates only. Check your school record and current official guidance when decisions matter.

Last reviewed: 27 June 2026 by Site editor and maintainer.

Reviewed as an independent explainer. For school-specific decisions, always check the school record and current official guidance.

Core formula: attended time divided by possible time, multiplied by 100.

A typical full-year benchmark is 190 school days or about 380 sessions.

Exact school figures can differ because schools may count sessions, codes and totals differently.

The attendance percentage formula

The core calculation is simple: attendance percentage equals attended time divided by possible time, multiplied by 100.

If you have days, use days in both parts of the formula. If you have sessions, use sessions in both parts. Mixing the two gives misleading results.

Attended days / possible days x 100
Attended sessions / possible sessions x 100

Days versus sessions

Many schools record attendance by session: one morning session and one afternoon session. That means one full day usually equals two sessions.

Session-based figures are often more accurate when there has been a half-day absence, late mark or medical appointment affecting only part of the day.

Why 190 days and 380 sessions are used

For broad UK attendance estimates, a full school year is often treated as about 190 teaching days. With two sessions per day, that becomes about 380 possible sessions.

These are working assumptions, not promises. School calendars, inset days, closures, adjusted timetables and the point you are at in the year can all change the exact possible total.

Year-to-date and future projection caveats

Projection tools only extend the maths from the figures entered so far. They cannot predict future attendance, changes to attendance codes, or whether an absence will be authorised.

Recovery estimates assume future attendance is complete for the run shown. Planned absence estimates add possible time without adding attended time.

Worked examples

Example one: 180 attended days out of 190 possible days gives 180 / 190 x 100, which is about 94.7%.

Example two: 361 attended sessions out of 380 possible sessions gives 361 / 380 x 100, which is 95%.

Example three: 19 attended days out of 20 possible days gives 19 / 20 x 100, which is 95%. Early in a term, one missed day has a larger effect because the total is still small.

Why exact school records may differ

A school may hold a different attendance total because it records sessions rather than days, includes partial absences, updates codes later or uses a different possible total for the period shown.

That is why this site presents all results as estimates for general information only. When the exact number matters, the school record should be treated as authoritative.