HEALTH & EVERYDAY
ISO week number calculator
Estimate ISO week from day of year.
Estimated result
Week 29
- ISO week-year
- 2026
Uses ISO 8601 week-date rules, including week-years that begin or end in an adjacent calendar year.
SOURCES & REVIEW
Checked against official guidance
Last checked 14 July 2026 · Rule version GB-2026.27.1
NHS: Healthy weight ↗COMMON QUESTIONS
Frequently asked questions
Is this an exact quote or tax return?
No. It is an estimate based on the inputs and assumptions shown.
When was this checked?
The method and linked official guidance were reviewed for the current UK release.