Week numbers 2027: every week at a glance

6 October 2026 · Calcosmo editorial team

Planning holidays, shifts or projects for next year? Below are all week numbers of 2027 with the Monday and Sunday of each week. For a single date, use the week number tool.

In short

• 2027 has 52 weeks.
• Week 1 runs from Monday 4 January to Sunday 10 January 2027.
• Friday 1 January to Sunday 3 January 2027 still belong to week 53 of 2026.
• The last week, week 52, runs from Monday 27 December 2027 to Sunday 2 January 2028.

All week numbers in 2027

Why doesn’t 2027 start with week 1?

Week numbers follow the ISO 8601 standard: weeks start on Monday and week 1 is the week with the first Thursday of the year. 1 January 2027 is a Friday, so the first Thursday is 7 January, and its week starts on Monday 4 January. The days before still count towards the last week of 2026, which is exactly why 2026 has 53 weeks.

Useful for planning

• School holidays and company shutdowns in Europe are often announced by week number. The table shows the dates straight away.
• Deliveries and production schedules often use week numbers. In international agreements, also mention the date, because the US counts weeks differently.
• Spreadsheets: =ISOWEEKNUM(date) in Excel or Google Sheets returns the same week number as this table.

Want to know which week it is today? Read what week it is right now or open the week number tool. It also works the other way round: enter a week number and year to see the dates.