Week dimension
Week is the dimension that groups events by the numbered week of the year (01–53). In GA4 the week begins on Sunday, so the first and last weeks of a year are usually partial. It smooths daily noise into a steadier trend, but the Sunday boundary and partial-week edges mean its counts are not directly comparable to ISO-week tools that start on Monday.
What this means
The week dimension assigns each event a week-of-year number, with GA4 treating Sunday as the first day of the week. Weekly grouping is the standard way to damp day-of-week swings and see a cleaner trajectory.
It sits between the date and month grains for trend work.
Boundary caveats
Because GA4 weeks start on Sunday and are numbered within the calendar year, week 01 and the final week are usually partial, so their totals look artificially small. Tools that use ISO weeks (Monday start) will number and bound weeks differently, so weekly figures will not line up one-to-one.
Account for partial edge weeks and the start-of-week convention before comparing.
- Week-of-year number, Sunday start in GA4
- Edge weeks are partial and look small
- Not aligned with ISO Monday-start weeks
How it appears in analytics and logs
A week value is the year's week number with a Sunday start. A low count in week 01 or 53 typically reflects a partial week at the year boundary, not a real drop.
Diagnostic use case
Use the week dimension to smooth daily volatility into weekly trends, remembering GA4 weeks start on Sunday and edge weeks are partial.
What WebmasterID can help detect
WebmasterID can roll events into weekly buckets first-party, giving smoothed trends without third-party tracking.
Common mistakes
- Reading partial edge weeks as real declines.
- Assuming GA4 weeks match ISO Monday-start weeks.
- Comparing week numbers across tools without checking the convention.
Privacy and accuracy notes
The week dimension records timing, not identity. WebmasterID aggregates events by week first-party without profiling visitors.
Related pages
- Date dimension
Date is the dimension that records the calendar day of an event in YYYYMMDD form, computed in the GA4 property's reporting time zone. It is the default x-axis of most trend reports. Its day boundary is the property's midnight, not UTC or the visitor's clock, so the same raw event can be assigned to a different date than another tool would choose.
- Month dimension
Month is the dimension that groups events by calendar month (01–12) in the property time zone. It is the coarse grain for seasonal and budget-cycle reporting. Its main pitfall is that months have different lengths, so raw month-over-month comparisons mix a 28-day February with a 31-day March, which can masquerade as a trend if you do not normalise per day.
- Nth week dimension
Nth week is the dimension that numbers weeks by their offset from the start of the selected range — week 0, week 1, and so on. It is the weekly analog of nth day, built for multi-week retention curves and cohort decay where you want week-1 retention to align across cohorts regardless of when each began. Its numbering is relative to the report's range and resets when the range changes.
- Web analytics
Smooth weekly trends first-party.
Sources and verification notes
- Google Analytics Help — [GA4] Dimensions, metrics, and other termsDefines week dimensions and their year-based numbering.
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.