How we calculate attendance

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.

Days-based estimates remain useful when users only know whole days missed, but sessions are usually closer to the way schools and MIS systems hold the official record.

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.

Term-to-date calculations can look severe early in the year because each missed day or session is sitting inside a much smaller possible total than a full-year benchmark.

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.

Rounding and display differences

This site rounds for readability, which means a result may be shown to one decimal place or as a rounded whole-number-style explanation depending on the context.

Schools or MIS systems may round differently, truncate values, or display a percentage based on session totals rather than a rough day-based estimate.

Why the result on this site may differ from your school app

A school app may use actual session totals rather than broad day-based estimates, may record partial-day absence differently, or may update attendance codes after the first entry has been made.

Authorised absence can still affect the displayed attendance percentage depending on how the school system reports it. That is why school and MIS records should be treated as the official source of truth.

About the England attendance comparator

Some calculator pages also compare a result with the latest published England attendance rate from Department for Education Explore Education Statistics. That comparator is optional context only and is hidden if the stored benchmark is missing, stale or malformed.

The current benchmark is an England-only academic-year-to-date figure for compulsory-school-age pupils in state-funded primary, secondary and special schools. It helps users answer a different question from the main calculator: not just what the estimate is, but how it sits against the latest national attendance picture.

It still has limits. The DfE release describes these figures as estimates and early indicators, and exact school records may differ because schools can use live session totals, part-day marks, later code changes or a different measurement period.

For the underlying source, see the latest DfE attendance release alongside the official resources page.

Examples showing the same absence at different points in the year

One missed day out of 20 possible days gives 95%, while one missed day out of 190 possible days gives about 99.5%. The absence is the same, but the running total is not.

Recovery works the same way in reverse. A fully attended day can lift the figure more visibly early in the year than it does once the total is already very large.

When users should check with the school

If a figure is being used in a meeting, letter, support discussion, attendance review or formal decision, users should check the exact school record instead of relying on a broad estimate alone.

The same applies when partial sessions, coding updates, part-time timetables or school calendar differences may affect the exact percentage shown.

Questions, corrections and source checking

If you think an example, assumption or external guidance link needs updating, contact support@schoolattendancecalculator.co.uk with the page URL and the issue you noticed.

The site can update explainers and assumptions, but it cannot verify a child-specific school attendance record. Those checks must come from the school or official source.