2027 Calendar with Week Numbers (ISO and US, Free)
Every week of 2027 with start and end dates, in ISO (Monday) and US (Sunday) numbering. 2027 has 52 weeks in both. Check any date with a free week number tool.
Published ยท 6 min read
2027 has 52 numbered weeks in both common systems. In ISO 8601 numbering (weeks start on Monday), week 1 runs from Monday 4 January to Sunday 10 January 2027, and week 52 ends on Sunday 2 January 2028. In US numbering (weeks start on Sunday), week 1 runs from Sunday 27 December 2026 to Saturday 2 January 2027. The full table is below, and the free week number calculator shows the same list for any year.
ISO or US: which does your calendar use?
- ISO 8601 is used across Europe and by many companies, factories and logistics firms worldwide. Weeks run Monday to Sunday, and week 1 is the week containing the year's first Thursday.
- US numbering is common in the US and Canada. Weeks run Sunday to Saturday, and week 1 is the week containing 1 January.
A delivery note that says "KW 14" (German for calendar week) means ISO week 14. When in doubt, put dates next to week numbers on anything you share.
What's different about 2027
- 1 January is a Friday. Under ISO rules, 1, 2 and 3 January 2027 belong to week 53 of 2026, because 2026 is a 53-week year. ISO week 1 of 2027 starts on Monday 4 January.
- Under US rules, 1 January is in week 1, which began on Sunday 27 December 2026.
- The year ends differently too. ISO week 52 ends on Sunday 2 January 2028. In US numbering, Sunday 26 December 2027 to Saturday 1 January 2028 contains New Year's Day 2028, so it counts as week 1 of 2028 (some calendars label it "53").
- For most of the year, the US number is one higher than the ISO number from Monday to Saturday. On Sundays they can differ by two.
Week numbers for some key 2027 dates
| Date | Day | ISO week | US week |
|---|---|---|---|
| 1 January | Friday | 53 (of 2026) | 1 |
| 26 January | Tuesday | 4 | 5 |
| 1 April (Indian financial year starts) | Thursday | 13 | 14 |
| 1 July | Thursday | 26 | 27 |
| 15 August | Sunday | 32 | 34 |
| 2 October | Saturday | 39 | 40 |
| 25 December | Saturday | 51 | 52 |
| 31 December | Friday | 52 | 1 (of 2028) |
2027 weeks with dates
ISO weeks run Monday to Sunday; US weeks run Sunday to Saturday. Dates without a year are in 2027.
| Week | ISO 8601 (Mon to Sun) | US (Sun to Sat) |
|---|---|---|
| 1 | 4 Jan to 10 Jan | 27 Dec 2026 to 2 Jan |
| 2 | 11 Jan to 17 Jan | 3 Jan to 9 Jan |
| 3 | 18 Jan to 24 Jan | 10 Jan to 16 Jan |
| 4 | 25 Jan to 31 Jan | 17 Jan to 23 Jan |
| 5 | 1 Feb to 7 Feb | 24 Jan to 30 Jan |
| 6 | 8 Feb to 14 Feb | 31 Jan to 6 Feb |
| 7 | 15 Feb to 21 Feb | 7 Feb to 13 Feb |
| 8 | 22 Feb to 28 Feb | 14 Feb to 20 Feb |
| 9 | 1 Mar to 7 Mar | 21 Feb to 27 Feb |
| 10 | 8 Mar to 14 Mar | 28 Feb to 6 Mar |
| 11 | 15 Mar to 21 Mar | 7 Mar to 13 Mar |
| 12 | 22 Mar to 28 Mar | 14 Mar to 20 Mar |
| 13 | 29 Mar to 4 Apr | 21 Mar to 27 Mar |
| 14 | 5 Apr to 11 Apr | 28 Mar to 3 Apr |
| 15 | 12 Apr to 18 Apr | 4 Apr to 10 Apr |
| 16 | 19 Apr to 25 Apr | 11 Apr to 17 Apr |
| 17 | 26 Apr to 2 May | 18 Apr to 24 Apr |
| 18 | 3 May to 9 May | 25 Apr to 1 May |
| 19 | 10 May to 16 May | 2 May to 8 May |
| 20 | 17 May to 23 May | 9 May to 15 May |
| 21 | 24 May to 30 May | 16 May to 22 May |
| 22 | 31 May to 6 Jun | 23 May to 29 May |
| 23 | 7 Jun to 13 Jun | 30 May to 5 Jun |
| 24 | 14 Jun to 20 Jun | 6 Jun to 12 Jun |
| 25 | 21 Jun to 27 Jun | 13 Jun to 19 Jun |
| 26 | 28 Jun to 4 Jul | 20 Jun to 26 Jun |
| 27 | 5 Jul to 11 Jul | 27 Jun to 3 Jul |
| 28 | 12 Jul to 18 Jul | 4 Jul to 10 Jul |
| 29 | 19 Jul to 25 Jul | 11 Jul to 17 Jul |
| 30 | 26 Jul to 1 Aug | 18 Jul to 24 Jul |
| 31 | 2 Aug to 8 Aug | 25 Jul to 31 Jul |
| 32 | 9 Aug to 15 Aug | 1 Aug to 7 Aug |
| 33 | 16 Aug to 22 Aug | 8 Aug to 14 Aug |
| 34 | 23 Aug to 29 Aug | 15 Aug to 21 Aug |
| 35 | 30 Aug to 5 Sep | 22 Aug to 28 Aug |
| 36 | 6 Sep to 12 Sep | 29 Aug to 4 Sep |
| 37 | 13 Sep to 19 Sep | 5 Sep to 11 Sep |
| 38 | 20 Sep to 26 Sep | 12 Sep to 18 Sep |
| 39 | 27 Sep to 3 Oct | 19 Sep to 25 Sep |
| 40 | 4 Oct to 10 Oct | 26 Sep to 2 Oct |
| 41 | 11 Oct to 17 Oct | 3 Oct to 9 Oct |
| 42 | 18 Oct to 24 Oct | 10 Oct to 16 Oct |
| 43 | 25 Oct to 31 Oct | 17 Oct to 23 Oct |
| 44 | 1 Nov to 7 Nov | 24 Oct to 30 Oct |
| 45 | 8 Nov to 14 Nov | 31 Oct to 6 Nov |
| 46 | 15 Nov to 21 Nov | 7 Nov to 13 Nov |
| 47 | 22 Nov to 28 Nov | 14 Nov to 20 Nov |
| 48 | 29 Nov to 5 Dec | 21 Nov to 27 Nov |
| 49 | 6 Dec to 12 Dec | 28 Nov to 4 Dec |
| 50 | 13 Dec to 19 Dec | 5 Dec to 11 Dec |
| 51 | 20 Dec to 26 Dec | 12 Dec to 18 Dec |
| 52 | 27 Dec to 2 Jan 2028 | 19 Dec to 25 Dec |
Every row was generated with the same code the week number calculator uses.
How to check any date yourself
- Open the free week number calculator. Today's week is shown at the top.
- Under Week numbering, choose ISO 8601 (Monday start) or US (Sunday start).
- In Week number for a date, pick a date in 2027. Early January dates can belong to the neighbouring year's week list.
- Read the week number and its dates underneath, or press Show all weeks of 2027 for the full list.
Planning ideas for 2027
- Sprints: two-week sprints that start on Monday 4 January line up with odd ISO week numbers: weeks 1-2, 3-4, up to 51-52.
- Payroll: 2027 has 53 Fridays, so a weekly Friday payroll has 53 paydays. See how many weeks are in a year.
- Deadlines: the free date calculator shows the gap to a date in weeks and days.
- Leave: see long weekends in 2027 in India and working days in 2027.
For how the ISO rules work, including why a year can start in week 53, read what week number is it.
Look up any week
Bookmark the free week number calculator for the year ahead. It shows today's week on load, switches between ISO and US numbering, and lists every week of any year with its dates, all in your browser.
Frequently asked questions
- How many weeks are in 2027?
- 52, in both ISO and US numbering. 2027 starts on a Friday and isn't a leap year, so it doesn't get a 53rd ISO week.
- When does week 1 of 2027 start?
- In ISO numbering, on Monday 4 January 2027. In US numbering, on Sunday 27 December 2026, because that week contains 1 January.
- What week is 1 January 2027 in?
- ISO week 53 of 2026, or US week 1 of 2027.
- Why are ISO and US week numbers different in 2027?
- The two systems start weeks on different days and define week 1 differently. In 2027, US week 1 starts eight days before ISO week 1, so the US number is usually one higher.
- What week is Christmas 2027 in?
- Saturday 25 December 2027 is in ISO week 51 and US week 52.
Calculators
Try the Week Number Calculator
Free, no sign-up, works in your browser. See today's week number at a glance, find the week number of any date, and list every week of the year with its dates.