Week Number Calculator
Find out exactly what ISO week it is today — or look up the week number, day of the year and days remaining for any date.
Know your week at a glance
Week numbers run a lot of the world's planning — sprint schedules, retail calendars, manufacturing and logistics all talk in "week 32". This tool gives you the current ISO 8601 week instantly and lets you check the week number for any other date, plus how far through the year you are.
How to use it
- Read today's current week at the top.
- Pick any date to see its ISO week and week-year.
- Check the day of year and days remaining for planning.
Where week numbers matter
- Project & sprint planning — "due end of W14".
- Retail & finance — fiscal week calendars.
- Manufacturing — production and date codes.
- Scheduling across teams and time zones.
Frequently asked questions
What week number is it right now?
The big number at the top is the current ISO 8601 week number for today's date, along with the ISO week-numbering year and the full date.
How is the ISO week number defined?
Under ISO 8601, weeks start on Monday and week 1 is the week containing the year's first Thursday (equivalently, the week containing January 4th). This is the standard used across Europe and in business and software.
Why can a date in early January be week 52 or 53?
Because ISO weeks belong to the week-numbering year, the first days of January can fall in the last week of the previous year. The tool shows the correct ISO week-year for exactly this reason.
Is my data private?
Yes. Everything is computed in your browser; no dates are sent anywhere.